Non-playable character

Non-playable characters (NPCs) are characters that cannot be played by the player from the game's start. They are in every Sim game: The Sims, The Sims 2 and The Sims 3. (While townies are considered to be a class of NPC, they are largely outside the scope of this article.)

There are two main types of NPC; ones that through relationships and/or simple cheats will be able to be playable characters without any programming errors and ones that were specifically not meant to be played. In The Sims, all NPCs, other than the townies, are of this second type. Sims cannot build relationships with them, and most either can't be interacted with at all, or only have a few interactions that are related to their function. In The Sims 2 and The Sims 3, most NPCs can be interacted with, at least when they're not on the job, and Sims can build relationships with them. Also, some may appear on community lots, where they can essentially be treated as townies.

The Sims
Except for the townies, NPCs in The Sims are not full-fledged Sims. They have special character files which contain their names and define their appearance, and which control what they can do and how (or whether) they can be interacted with.

Service NPCs
These NPCs can be hired to perform services around the house.


 * Maid: When hired, Brigit the Maid will visit everyday to clean the lot. She will clean dishes, pick up trash, mop up puddles and make beds.


 * Gardener: Every three days Gardener Gloria will arrive to water indoor and outdoor plants.


 * Repairman: When summoned Repairman Bruno fixes broken objects, unclogs toilets, and even replaces light bulbs.
 * Pizza Deliverer: Offers a one-off pizza delivery service to your Sims' home when called. Oddly, his dialogue box reveals his name to be "Freddy the Pizza Delivery Dude", but if Hot Date is installed, his rollover text will read "Pizza Delivery Dude Dale". This contradiction remains unfixed in the final version of the game.


 * Caterer: Yves the Caterer can be hired for parties, and will refill the punch bowl, restock the buffet table, clear empty plates and socialise with guests.


 * Animal Control: Animal Control Evan can be hired to remove El Bandito or Henri LeStanc. He cannot be called unless one of the two is on the lot.


 * Butler: Alfred the Butler works from 7am until 12am every day and will cook, clean and look after babies and pets. He may also hire additional service NPCs to assist him, or activate Servo when needed.

Other NPCs

 * Paper Girl: Nancy the Paper Girl appears on the lot at 9am every morning to deliver the newspaper and tabloid. If a family has a dog, the dog may scare away the paper girl, but she will make her deliveries first.


 * Postal Woman: Carrie the Postal Woman appears every 3 days to deliver bills, which she places in the mailbox.


 * Repo-man: If bills go unpaid for any reason, the repo man will arrive and repossess objects from the lot to cover the value of the bills.


 * Social worker: If babies are not properly taken care of, Sylvia the Social Worker will appear to take them away.


 * Burglar: Whenever every Sim on the lot is asleep, Some Sneaky Sim may sneak in and steal their possessions. Players can either have a Sim call the police, or buy an alarm. With the alarm installed, the police will arrive instantly. If the police are called over the the phone, it may take too long for them to arrive, and the burglar may escape.


 * Grim Reaper: The Grim Reaper appears when a Sim dies to claim their remains. If Death is in a good mood however, another Sim can be directed to challenge him, although children can't plea with the Grim Reaper. If he accepts, he will either play rock, paper, scissors with or a shell game. If the Sim wins the game, the deceased is brought back to life for a second chance, but if the Sim loses, Death will either take the corpse or create a zombie. When the Sim is turned into a zombie, they will have no personality and their skin will be coloured green.


 * Tragic Clown:, Sunny the Tragic Clown will visit depressed Sims who own the "Tragic Clown" painting in order to cheer them up. However, your sims' moods will not improve as the Tragic Clown is also feeling miserable. The clown will usually walk around the house, and do nothing but cough and cry, and fail at any tricks (i.e, when he juggles, he hits himself with his bowling pins and when he blows up a balloon poodle, it will pop). He will leave when the depressed Sim's Fun need increases, or when the Tragic Clown painting is either sold or destroyed.


 * Santa Claus: If a Christmas tree and a plate of cookies are near a fireplace at midnight, Santa Claus will appear while the Sims are sleeping. He'll leave a small gift for each Sim in the household, plus an extra special present, which could be any item.


 * Entertainer: Chip or Bunny can be hired to emerge from the giant cake, and start entertaining party guests. There is a chance that the entertainer might stir jealousy from other sims, and children will be shooed out of the room.


 * Mime:, Gabby the Mime will show up at a party if it is going very badly. Like the Tragic Clown, he will try to raise everyone's mood, but isn't very good at it and may occasionally steal objects on the lot. He will leave only when the party gets better.


 * Party crasher: Pete Dropinsky or Paulette Dropinsky may arrive during mediocre to fairly good parties, and will socialise with other guests. They may possibly destroy objects on the lot.


 * Drew Carey: A real life celebrity who shows up as a reward for a great party.


 * Obsessed fan:, Sims can attract unwanted attention if they achieve 3 stars of fame or more. The obsessed fans will stalk the Sims wherever they go, at home or at work. They leave 'special presents' for the Sims - black roses. They also paw through garbage cans, and will steal any awards that Sims have won for acting, singing or modeling. Awards can be protected by placing them in a room with the Zeddy-Lock Celebrity Security Door, as Obsessed Fans cannot go through that door.


 * Celebrities: Marilyn Monroe, Christina Aguilera and Avril Lavigne may appear at random on lots in Studio Town.


 * Downloadable Celebrities: Sarah McLachlan, Freddie Prinze Jr., Jon Bon Jovi, Richie Sambora and Elle Woods are downloadable NPCs for Superstar, appearing in Studio Town when installed.


 * Mystery Man: The Mystery Man will appear on all residential lots shortly after a family moves in, or when a family is loaded after installing Makin' Magic. He will leave a package containing magic-related objects and ingredients. He also appears on all Magic Town lots, where sims can purchase or sell wands. The Mystery Man also acts as the Spellchecker, delivering citations to Sims who cast spells in front of non-magical sims.


 * Wally and Molly O' Wisp: Brother and sister spirits who appear when the "Of House and Home" charm is used. Wally will quickly clean the house if summoned, while Molly will wreak havoc.


 * Gardening gnomes: When enchanted, Gnomes will come to life and take care of plants on the lot.


 * FlaminGoGo Dancers: When enchanted, Flamingo sculptures will come to life and socialise with other Sims on the lot, making them potential party entertainers.

Community lot NPCs
All community lots in The Sims spawn a janitor, who does general clean-up and repair work on the lot. Community lots on Vacation Island, and in Studio Town and Magic Town, also spawn a "lot director" who can provide information about some aspects of gameplay. On Vacation Island lots, a costumed mascot will arrive in the morning and leave at night, and an indoors maid will appear if a hotel desk is present.

Other community lot NPCs such as clerks, cashiers, waiters, etc., are spawned by specific objects.

The Sims 2
The Sims 2 NPCs are much more colorful. For starters, basic NPCs can be interacted with in the same ways that other Sims can, at least when they're not on the job. They can be talked to, befriended, invited over, married, etc. They can be male or female, and each has a different face, hair color and name. They generally make more logical decisions, though there are exceptions. A neighborhood will usually have three NPCs of any given type (maid, etc.). If an NPC dies, becomes playable or gets turned into a vampire or werewolf, a new NPC will be generated to take the old NPC's place. An NPC that becomes a Witch however will continue to do their job, although this can only be done while they're off-duty and it's inconsistent whether they will wear their uniforms or their witch clothes. When University is installed, every NPC and townie get memories of going to college.

Townies
Townies form the largest class of NPC. Townies wander around the neighborhood or randomly walk by Sims' houses. There are many types of Townies in The Sims 2: see Townie for more information.

Service NPCs
Service NPCs are NPCs that help Sims around the house.
 * Maids: Maids clean the house and do most of the housekeeping. They come every day.
 * Gardeners: Gardeners clean Sims' gardens, pull weeds, water flowers, trim shrubs, and rake falling leaves. They come every three days.
 * Nannies: Nannies take care of babies, toddlers, and children. The player can have them track the calling Sim's work schedule. It's important to hire a nanny if there's no teen or older Sim in the house, as the social worker will take children who are left unattended. Nannies are also needed when going to a community lot or going on vacation would leave children home alone.
 * Bartenders: Sims can hire a bartender if they have a bar in their home. They are paid by the hour. Bartenders are also Community Service NPCs. Bartenders working at home and community lots are different bartenders.
 * Exterminators: Whenever a Sim's house is infested with cockroaches, they can call exterminator to get rid of them.
 * Repairmen: Sims can call a repairman to fix broken objects. They'll fix everything from clogged toilets to broken electronics. They even tune pianos. Whenever a Servo is broken and he/she lives alone, a repairman will automatically come to fix it.
 * Gypsy Matchmaker: Gypsy Matchmakers sell potions to Sims. Sims can buy love potions, or potions to cure Vampirism, Lycanthropy, PlantSimism, or Witchiness. Sims can also ask the Matchmaker for a blind date. In FreeTime, the Gypsy Matchmaker may deliver a Dusty Old Lamp to Sims with high enthusiasm in a hobby, and high Lifetime Aspiration.
 * Obedience Trainers: Obedience Trainers train adult pets and sell Lycanthropic-B potions.
 * Animal Control Officers: Animal Control Officers dress like Police, and they're often mistaken for the same person . They come to bring the newly adopted Pets for the family, or take away untreated Pets from the family.
 * Butlers: Butlers take over almost all of the Service NPCs work. So, Sims no longer need to hire every single Service NPC for housekeeping. Butlers are very costly, so players should mind a family's budget before having them hire one. Butlers don't take care of some problems, such as cockroaches, fires, or burglars. Instead, they call the appropriate NPCs.
 * Landlords: Landlords are assumed to be the owners of the apartment lots. Sims can pay the weekly rent directly to the landlords or by using the mailbox. Sims can lower their rent by making friends with them. They will garden and clean the common area in an apartment lot.

Emergency NPCs
Emergency NPCs arrive immediately after Sims call them on the phone, or when summoned by an alarm.
 * Police: Police can apprehend a burglar, but are not always able to. They also appear when a Teen is caught sneaking out or a party lasts until midnight. Sims also need to call the police when their Teens or pets run away. In University, a police officer wearing a llama blazer will "arrest" Sims who are to be inducted into the Secret Society.
 * Firefighters: Firefighters are always able to put out fires, though when a fire is very large, they sometimes call for help from other firefighters.

Other Service NPCs
Other than hired Service NPCs, there are also some Service NPCs who come on some occasions.
 * Social Workers : A Social Worker come when any babies, toddlers, or children are left unattended for a period, have critical needs, or become too cold or too hot, and will take them away. They also come when a family adopts a child.
 * Repo Men: If bills are left unpaid for 3 days, a Repo Man will come to take away some of a family's objects to cover the bill.
 * Mail Carriers: Every Tuesday and Thursday, a mail carrier will come to a Sim's house to deliver bills. (In college sub-neighborhoods, the mail carrier comes every 3 days.) Mail carriers also come to take paid bills.
 * Newspaper Boys/Girls: Often called "Newsie". They deliver the newspaper every morning, and also deliver hobby magazines. They are always teenagers.
 * Carpool Drivers : Carpool Drivers are the ones who drive the carpool and school bus, fly the helicopter, etc.
 * Pizza Deliverers: They deliver pizza when a Sim orders one.
 * Chinese Food Deliverers: Just like pizza deliverers, only they deliver Chinese Food.
 * Delivery Men: They deliver most of the things, other than bills, newspaper, pizza, and Chinese food. In the base game, they deliver groceries. FreeTime expanded their functions so they also bring novels (when a Sim finishes one), photo albums, and photo snapshots.
 * Bellhops : Bellhops appear on hotel lots, and will be at the podium in the hotel lobby. Players can click on a them to have Sims check in and check out. They also deliver room service to the Sims' room.
 * Housekeepers: Housekeepers clean the messes Sims make and fix broken things in their hotel room. They arrive in the hotel in the morning and leave at night. Sims can keep them away by putting "Do not disturb" on the door.

Community Service NPCs
Community Service NPCs are Service NPCs who serve Sims on community lots.
 * Cashiers: Cashiers are always teens. Whenever there's a cash register on an unowned community lot, they will occupy it. Although they appear to be very skilled in cashiering, if Open for Business is installed, they may not have a talent badge in operating a cash register.
 * Cafeteria Chefs: They work in dorms or community lots in college sub-neighborhoods, if a ShinyTyme Cooktop is present.
 * Baristas: They serve Sims at espresso bars on community lots. They are similar to Bartenders.
 * Hosts: In restaurants, hosts greet Sims at in the podium, and seat them at any available table or bar.
 * Servers: Servers are the waiters or waitresses in a restaurant. They wait on Sims, bring their food, and clean tables and dirty floors.
 * Cooks: Cooks prepare the dishes in restaurants. Unlike other Service NPCs, they cannot be interacted with.
 * DJs: If there's a DJ booth on a community lot, a DJ will operate it. Playable Sims can also work for a while as a DJ and earn simoleons.
 * Stylists: When there's a vacant salon chair in an unowned community lot, one of these Sims will take over the salon chair, and will be able to give Sims makeovers. They may not have talent badges in Cosmetology.
 * Masseuses: If there's a massage table on a community lot, a masseuse will use it. Sims can purchase a massage from them, and they will gain comfort and energy needs. Special massages can be purchased or learned in every vacation destination.
 * Local Chefs : Local Chefs cook food for Sims whenever there is a Food Stand on a community lot. There are four kinds of Local Chefs: Mountain, Far East, Tropical, and Diner. Each Local Chef prepares different food.
 * Fire Dancers : If there's a fire dance mat on a community lot, there will be a Fire Dancer. Sims can watch them fire dancing or study fire dancing from them. They are mainly available in Twikkii Island, but they can be available anywhere as long as a fire dance mat is on the lot.
 * Tour Guides : Tour Guides appear in every community lot and hotel lot in any vacation destination. Sims can book tours from them, and when they do, a vehicle immediately arrives to pick them up.
 * Human Statues : When Poised Podium by Performance Arts is placed on a community lot, a Human Statue will appear there. Sims can watch them or give them tips.
 * Break Dancers : If there's a break dance mat on a community lot, there will be a Break Dancer. Sims can watch them break dancing or study break dancing from them. They are similar to Fire Dancers.

Wandering NPCs
These NPCs usually wander around the town, or even walk by Sims' houses.
 * Professors: Professors are elder or adult Sims that young adults meet when they go to their first class in a college major. Each major has two professors, one male, one female. They can be interacted with normally, but college students can gain class performance by building relationships with the professors in their major. Playable students can also ask the professors in their major for tutoring, but that decision must be made by the player. Professors may appear on community lots outside of the college sub-neighborhood, and sometimes appear on secret hobby lots.
 * Coaches: Coaches sometimes appear on a lot, whether it's a college community lot, dorm, Greek house, or even a private rental house. They will yell at Sims and try to force them to work out, but can often be avoided.
 * University Mascots: There are two types of mascots. One is the llama mascot, who appears to be a costumed male version of the cheerleader. The other is the evil mascot, who is dressed as a cow. They may appear on any lot in a college sub-neighborhood. The llama mascots will autonomously do the school cheer in front of any Sims. The evil mascots will do pranks, will irritate and annoy Sims, and may even do some flirting. When the llama and cow mascots see each others, they will fight. The llama mascots will always win because their Body skill is maxed, while the cow mascots have little or no body skill.
 * Cheerleaders: Cheerleaders are similar to llama mascots, except that they are always female and do not wear full-body costumes.
 * Streakers: Streakers streak in any lot in a college sub-neighborhood. Other Sims will be shocked when they see the nude streakers. Unlike most NPCs, they cannot be interacted with.
 * Mrs. Crumplebottom : This cranky, strict old woman can be seen in any community lot in Downtown. Mrs. Crumplebottom hates to see two Sims are doing romantic social interactions in public. When she sees any, she will beat them with her purse. She will ruin any dream date, making it into a bad one. She will also lecture any Sims who are wearing undies or swimsuits, or are naked.
 * Dateable Slobs: These slobs are very mean and sloppy. They can only be found in Downtown or on Secret Hobby Lots. Slobs are easy to recognize since they wear very dirty clothes.
 * Mr. Big &amp; The Diva: Mr. Big and The Diva have different (randomly generated) names in each neighborhood, but they always have the same appearance. Mr. Big wears a red lounge suit and has neat hairstyle, while The Diva wears black dress with red scarf, and has long hair. They are Downtownies and very rich, but also mean. If they move into a family, they will add §70000 to the family funds.
 * Grand Vampires: They are the leaders of the vampires in Downtown, and can only be found in Downtown at night. Grand Vampires have a bluish skin tone, red eyes, and fangs. They have the pleasure aspiration. Grand Vampires always have the prefix "Count" in their name if male and "Contessa" if female. If playable Sims makes friends with them, they can bite those Sims and turn them into vampires.
 * Wolves: Wolves are a unique breed of large dog, but are slightly different from dogs. Wolves may wander around a lot, and can be summoned by a werewolf.
 * Pack leaders: Pack Leaders appears as a wolves with black fur and glowing yellow eyes. If a Sim makes friends with them, they can nibble that Sim, and he or she will become a werewolf. They mostly appear at night. They can be greeted and interacted with, but they usually break things and make messes. They also can't be taught any commands or be given commands. Pack Leaders have their own names.
 * Stinky Skunk: Stinky Skunk wanders around residential lots. Sims may pet him, watch him, or chase him off, though the former two actions will cause him to spray them. If sprayed, Sims will get a negative memory, have an empty hygiene bar, and will be a subject of gossip. Pets can also be sprayed.
 * Penguin: Penguins may appear at a house if it's snowing, there's a snowman in the lot (Whether finished, unfinished, or broken), or a fish is mounted on the wall. He will talk to the snowman for hours and leave. Sims can pet him or shoo him. If he's unhappy, he will leave the house or may eventually pee himself.
 * Unsavory Charlatan : He appears in all community lots frequently. He is a pickpocket, and cannot be interacted with. He may autonomously greet any Sims, and may eventually pick their pocket. Sims with high logic skill may prevent it. If the Sims became his victim, they can attack him or report it to police using the phone.
 * Ninjas : Ninjas only appear randomly in Far East Vacation Destination Community Lot. Sims can learn to teleport by answering a questions from Ninjas, much like Chance Cards. Ninjas always teleport here and there in a lot, and then disappear, so it's quite hard to approach them.
 * High Witches: There are two High Witches, Good and Evil. Sims who make friends with one can ask to be turned into a witch. They appear on every community lot, including those in college sub-neighborhoods. The Good Witch will cast Beautificus Locus and summon a Good Spectral Cat when arriving in a lot, while the Evil Witch will cast Corruptus Locus and summon an Evil Spectral Cat. When both Witches appear at the same time, they will usually fight each other.

Special NPCs
Special NPCs come when a special or rare occasion occurs.
 * The Grim Reaper : The Grim Reaper only appears when there's a dead Sim on a lot. Most of the time, Sims can plead with the Grim Reaper to bring the dead Sim back to life, unless they died of old age, drowning, or have been eaten by Cowplant. When a Sim dies of old age happily, The Grim Reaper will appear with 2 Hula Zombies accompanying him.
 * Hula Zombies : Hula Zombies appear only when a Sim dies of old age. They will dance hula while The Grim Reaper escorts the dead Sim. Their face resembles Bella Goth a lot.
 * Social Bunnies : If there's a Sim with critical social need, a Social Bunny will hop and appear in front of the lonely Sim. Only the Sim with low social need can see them. Sims can interact with them, friendly or mean. Either way, Social Bunny will fill up the social need by any interaction. When the need is halfway to full, they will hop to disappear. There are 3 colors of Social Bunnies: pink, blue, and yellow.
 * Headmasters: Headmaster appear when Sims invite them to send their children or teens to private school. They will arrive for dinner at 5 PM. The Sims need to schmooze and impress him in order to get his approval to send the children to private school.
 * Burglars: Burglars steal things from homes. On rare occasions, a burglar appears at night and steals something on the lot. Sims can't apprehend a burglar themselves. Players can buy a burglar alarm or get a Sim to call the police. The police officer will attempt to apprehend the burglar, but may lose the fight, in which case the burglar will get away. However, if the police officer wins, the victims will get a reward for catching the burglar.
 * Therapist: Often called Sim Shrink. When there's a Sim with critically low aspiration, the Therapist will appear. Only the Sim with aspiration failure can see him. He will help the Sim to push their aspiration a bit higher. After that, he'll be gone.
 * Reporters: Reporters come to owned business lots, browse the shop, and score it. If the owner can impress the reporters, they will give it a positive review, or maybe even the Best of the Best Award. Reporters don't have a fixed uniform, so it can be hard to tell who they are, unless they are seen taking notes.
 * Bigfoots: Bigfoot can be found in Hidden Burrow, the secret lot in Three Lakes. They have maximum skills and gold in every talent badge. When Sims make friends with them, Bigfoots will give them Bigfoot hug, and they will get a "Befriended Bigfoot" vacation memento. If Sims become best friends with a Bigfoot, they can ask him to move in, and another Bigfoot will be generated.
 * Wise Old Man: The Wise Old Man can be found in Pagoda in the Shadows, the secret lot in Takemizu Village. He will tell the dragon tale story. Sims who listened to the story can tell it to other Sims, and they will get a vacation memento. Sims must serve tea or bow to Wise Old Man, and then perform Tai Chi with him in order to be told the dragon tale story.
 * Witch Doctor: Despite the name, he's not a witch. The Witch Doctor can be found in the Mystery Hut, the secret lot in Twikkii Island. On arriving there, all his appliances and plumbing are broken. He will be relaxing in his hammock, and Sims can offer to help him. After a Sim is done fixing his broken stuff, he will give them a voodoo doll, and they will get a vacation memento. However, if the Sim didn't accept the doll, or was too slow to accept it, or the player canceled the interaction, the Witch Doctor won't give the voodoo doll again, unless the Sims reenter the lot.
 * Pirate Captain Edward Dregg: The Pirate Captain appears in the pirate ship if Sims plunder the captain's cabin. When befriended, he will teach Sims to sing a sea chantey.
 * Hobby Instructors: Each hobby has its own instructor. Hobby instructors can be met when a Sim gains 5 levels of enthusiasm in a specific hobby, has gained maximum hobby enthusiasm, or is in the hobby club. When they're on the secret hobby lot, Sims can ask the instructors for instruction in their hobby.
 * Rod Humble : Whenever a new family or household moves in (merging families does not count), or a family is played for the first time, Rod Humble will appear, deliver a new computer with The Sims 3 game in it, and leave. He will not appear if the player is currently playing in a college sub-neighborhood.
 * Spectral Assistants Both Good and Evil Witches can summon a Spectral Assistant, each with different purposes. Good Witches can summon one by using the Apello Servantus spell. The Spectral Assistant will help clean the house and garden, like a maid and gardener combined. Evil Witches can summon another by using Servantus Attackum. The Spectral Assistant will attack the intended Sim.
 * Spectral Cats: Also known as Feline Familiar. A witch can summon a Spectral Cat by using the Apello Cattus Amicus spell. The Spectral Cat's alignment depends on the alignment of the caster. Each witch can only summon one Spectral Cat, and the cat will always be the same if summoned again. Spectral Cats will behave like common cats, with some exceptions. In particular, they don't have the bladder need, can't get a job, don't age, and can't have litters.
 * Santa Klaus : Often being mistaken as Santa Claus. He will appear if there is a fire in the fireplace and there's a Santa Cookies in the same room as the fireplace. He will automatically become best friends if a Sim interacts with him.
 * Father Time : When throwing a New Year Bash, Father Time will appear on the sidewalk around 11 PM. He will occasionally make a ruckus and other Sims will react to it. At midnight, he will turn into Toddler New Year.
 * Toddler New Year : Father Time will eventually turn into Toddler New Year at midnight. Toddler New Year will autonomously smustle dance and fade away.

Other NPCs
Some NPCs only appear as thumbnails, cannot even be met. and never appear in the game. NPCs in this category are not included in any category above.
 * Pollination Technician : If an adult, male Sim who is more than 5 days away from becoming an elder is abducted by aliens, he will get home impregnated by Pollination Technician, and will give birth to a half-alien baby. Pollination Technician will appear in the child's family tree, but is not a real Sim. It's actually a set of genetics which is given to the half-alien baby.
 * ideal plantsim : When a PlantSim spawns a sporebaby, the baby will inherit genetics from the father/mother and ideal plantsim. Like Pollination Technician, ideal plantsim is actually a set of genetics, not an actual Sim.
 * Weather : Weather is a the weatherman of the forecasting channel in the TV. He predicts the incoming weather that could probably happen. Sometimes the Weather tells some funny jokes, but at others, he is rather resentful.
 * Genie Midlock : Though Genie can be met in the game, he is hardly any Sim. He grants 3 wishes to the Sim after they have the Dusty Old Lamp, then leaves, whether the wishes succeed or fail.

Invisible NPCs
There are some objects that move because there's an invisible NPC makes them do so. The name of these NPC's are visible upon using the Tombstone of Life and Death.
 * NPC - Remote Control Car : The remote control cars, both from base game and FreeTime, and also the remote control helicopter is being controlled by this NPC.
 * NPC - Robot : All the crafted robots except Servo are being controlled by this NPC whenever they're turned on.
 * NPC - Bird : When the bird cage is left open, the bird might fly around the room, which is controlled by this NPC.
 * NPC - Penguin : The truth is: Penguin is an object with animations; not a Sim nor a pet. Thus, this "object" is being controlled by this NPC to make it move.

Removed NPCs

 * Big Boss: An NPC called the Big Boss was originally intended to be included as part of the Killed Boss scenario however both the scenario and NPC were cut from the final game and are now only referenced in unused gamefiles.

Playability
Many NPCs in The Sims 3 can become playable, mainly through befriending them and inviting them into the active household. Since The Sims 3: Late Night the CharacterImport.xml in world files has been tuned to specify preferred NPC roles for homeless Sims.

For a full list of ways to make NPCs playable see Turning a Townie into a Playable Sim.

Townies

 * Townies - In The Sims 3 townies are simply all Sims that are not in the active household. Townies can be residents in other households, they can be homeless, or they can be part of the invisible Service NPC household.

Service NPCs

 * Maid - In premade worlds such as Sunset Valley maids are premade, otherwise they are randomly generated. Maids carry the Makes No Messes hidden trait, and are often Flirty or Kleptomaniacal. The maid service recurs until it is cancelled.
 * Repairman - In premade worlds such as Sunset Valley repairmen are premade, otherwise they are randomly generated. They can be phoned when plumbing and electronic devices break down.
 * Babysitter - In premade worlds such as Sunset Valley babysitters are premade, otherwise they are randomly generated. They are always teens and are also often kleptomaniacs.
 * Adoption Service - In premade worlds such as Sunset Valley adoption service workers are premade, otherwise they are randomly generated. They are rare and usually only appear when bringing new adopted children to a lot.
 * The Pizza Man/Women - Delivers pizza. In official towns they are premade Sims that as time goes by are replaced by randomly generated Sims. They have the Pizza Appreciator hidden trait, which allows them to get the powerful "Amazing Meal" moodlet from eating pizza.
 * Butler - In Bridgeport there are several premade butlers, otherwise these service NPCs are randomly generated. They have black uniforms and will do many different tasks: cooking, cleaning, massaging, putting out fires, repairing broken objects, fighting burglars, and helping with children. Butlers are a very expensive service and require a bed to sleep in.
 * Mixologist - These bartenders can be hired for parties. In Bridgeport they can be premade Sims, otherwise they are likely to be randomly generated.

Emergency NPCs
These Sims will normally stick around to patrol the house after their job is done allowing Sims to talk to them.
 * Police - When a burglar appears on the playable lot and an alarm is installed, they will arrive soon after and fight the burglar, but without an alarm they can be called. However, calling the police when there's no burglar will fine the Sim §500.
 * The Fire Department - Sims with a low cooking skill that attempt to cook anything involving an oven or a microwave will sometimes cause a fire. A fire can also be started by lighting a fireplace with flammable objects nearby, or a birthday cake can spontaneously combust. The fire alarm should alert the fire department whenever there is a fire, but they can also be phoned. Prank calling them when there is no fire will cost Sims a §500 fine.

Visiting NPCs

 * Grim Reaper - These randomly generated Sims are difficult to make playable. They only appear to take away Sims that have just died. At rare occasions they will stay around the house allowing Sims to talk to him. There was a bug that allowed Sims to woo the Grim Reaper and have children with him, but that has been fixed in a patch.
 * Burglar - A burglar appears at night when Sims are sleeping or out on the town. A Sim can befriend them by choosing to "Set Free" shortly after the police have made their arrest, allowing them to become acquainted so that Sims can call them on their own time. However, befriending burglars does not stop them from stealing from the sim. Burglars will be in the Criminal career track; playable sims can also become burglars. NPC burglars carry the hidden Burglar trait, which allows them to sneak.
 * Child Protection Worker - In premade worlds such as Sunset Valley they are premade, otherwise they are randomly generated. They take neglected children away from active households.
 * Paper Delivery - Appears every morning to deliver the papers. Can either be male or female, but is always a child. In official towns they are premade Sims that as time goes by are replaced by randomly generated Sims.
 * Mail Delivery - They are the people that deliver the bills in the mail. In official towns they are premade Sims that as time goes by are replaced by randomly generated Sims. They also deliver mail such as smelted metals, cut gems, mounted fish, and complimentary copies of books.
 * Science Geek - Science Geeks are very rare. In official towns they are premade Sims that as time goes by are replaced by randomly generated Sims. They will visit lots during a certain move in scenario.

Wandering NPCs

 * Tourist - Tourists are Sims from other locations who are visiting foreign worlds like Shang Simla. Tourists can be any Sim that does not live in the active world, so Sun Young Kim can be a tourist in Sunset Valley and Cornelia Goth can be a tourist in Shang Simla. Tourists can also be explorers.
 * Explorer - Explorers are tourists from other adventure neighborhoods that appear in whichever one the active Sim is visting. For example, Sun Young Kim from China may appear as an explorer when a Sim visits Egypt or France.They wear tan and khaki explorer outfits and visit tombs and graveyards.
 * Paparazzi - Paparazzi are recruited from the pool of homeless premade Sims and if there are not homeless then they are randomly generated. They follow celebrities and take photos. They are very difficult to interact with. However, there is a bug that sometimes makes them clones of premade and player-made Sims.

Community Lot NPCs

 * Location Merchant - These NPCs are recruited from residents, not from the pool of homeless Sims. They only appear naturally in adventure worlds, but can appear in base neighborhoods that have World Adventures cash registers placed on community lots.
 * Consignment Specialist - A resident Sim who works at the Consignment store. Since the consignment specialist is a randomly picked Sim, even sims in the neighborhood can work there. If the Consignment Specialist is moved in via Edit Town, he/she loses the job.
 * Tattoo Artist - Tattoo artists can give Sims tattoos. Tattoo artists are recruited from the pool of homeless Sims. Tattoo artists appear on community lots that have a tattoo chair placed on them. Tattoo artists always have lots of tattoos on their body.
 * Bartender - These mixologists are different to the service ones; they are recruited to Bars on community lots. Bartenders are recruited from the pool of homeless Sims and if there are no homeless then they are randomly generated.
 * Bouncer - Bouncers guard doors with velvet ropes placed before them. They can be bribed for entry. Bouncers are recruited from the pool of homeless Sims and if there are not homeless then they are randomly generated.
 * Proprietor -
 * Pianist - Pianists are recruited from the pool of homeless Sims and if there are not homeless then they are randomly generated.
 * Stylist - Stylist NPCS appear on community lots with at least one styling station on them. They wear a trendy outfit and will makeover a Sim for 175 simoleons. Active Sims can also interact with them to join the Stylist career. They are recruited from the pool of homeless Sims.

Other NPCs

 * Carpool/Taxi Driver/School Bus Driver - These Sims are never playable and always randomly generated. They are not drawn from the homeless pool.
 * Mummy - NPC Mummies are randomly generated in tombs from sarcophagi. They have unique mummy-like names and cannot be made playable. Playable mummies are made by turning active Sims into a mummy or by summoning one with relics.