Theme

Each expansion/stuff pack for The Sims is centered around one or more themes.

Family
Family is the main theme of The Sims: Livin' Large and The Sims 3: Generations. While Livin' Large doesn't primarily focus on the interaction between families, it introduced several new features at a time when the series was new. Meanwhile, the main focus of Generations is on the family, where family time is made more elaborate, and Sims are meant to "Live the Life to the Fullest". The Sims 2: Family Fun Stuff adds items related to family and children into The Sims 2.

Party
Parties are the main focus of The Sims: House Party, in which the ability to throw a party was introduced for the first time. Parties are also enhanced in The Sims 3: Generations, where there are even more types of parties. The Sims 2: Celebration! Stuff, The Sims 4: Luxury Party Stuff and The Sims 4: Spooky Stuff provided more party objects for The Sims 2 and The Sims 4, respectively. More varieties of parties were released with The Sims 4: Get Together. The Sims 4: Movie Hangout Stuff its main focus isn't party, but Sims can invite a couple of Sims to watch a movie together.

Dating
Dating is the main theme of The Sims: Hot Date, as well as one of the themes that come in The Sims 2: Nightlife, and again, The Sims 3: Generations. The dating feature enables two paired Sims to spend their time together doing romantic activities.

Vacation
The Vacation feature is introduced in The Sims: Vacation, and is the main theme in The Sims 2: Bon Voyage, The Sims 3: World Adventures, The Sims 3: Island Paradise, and in The Sims 4: Outdoor Retreat. The main purpose of this theme is to show Sims other parts of the world in their respective games, and to give them ways to spend their time and relax while on vacation. World Adventures primarily focuses on exploration and adventuring while Island Paradise primarily focuses on relaxation and vacations. The Sims 4: Outdoor Retreat focuses on camping, similar to vacationing in Three Lakes in Bon Voyage.

Pets
Pets is a theme used in many games throughout The Sims series. Sims can keep pets as part of their life in The Sims: Unleashed, The Sims 2: Pets, and The Sims 3: Pets. Pets are also featured in many console games; as seen here.

Fame
Fame is the main theme in The Sims: Superstar and The Sims 3: Showtime, as well as one of the themes in The Sims 3: Late Night. Sims are able to work in the Fame career, become celebrities, or become performers to pursue their desire to become famous. The Sims 3: Movie Stuff adds various themed items and outfits from popular Hollywood film genres.

Magic
Magic appears as the main theme in The Sims: Makin' Magic, and is a theme in The Sims 2: Apartment Life. Magic is reintroduced in the The Sims 3: Supernatural, via fairies and/or witches and wizards.

College
The college theme is only featured in The Sims 2: University and The Sims 3: University Life, where Sims can seek and pursue further education at college. While at college, Sims will also encounter and experience the college life: throwing parties, joining a Greek house, or studying.

Nightlife
Nightlife is the main theme of The Sims 2: Nightlife and one of the main themes in The Sims 3: Late Night. The theme of nightlife focuses on after-dark activities that involve visiting downtown or going to various clubs and lounges in the city, along with other vital roles of these expansion packs, such as vampires. The Sims 4: Get Together also has a few aspects of nightlife.

Profession and Business
In addition to going to work in careers, Sims can run businesses or perform jobs in a profession. These features enable Sims to earn money in ways other than just going to work with adequate skills. Sims can now be seen, and controlled, as they perform the work in their profession or business. This theme is mainly in The Sims 2: Open for Business, The Sims 3: Ambitions, The Sims 4: Get to Work and The Sims 4: Dine Out.

Weather
Seasonal activities and the seasons as well are introduced in The Sims 2: Seasons, where precipitation, such as rain and snow, will occur. Holiday themes also appears in The Sims 2: Holiday Party Pack and The Sims 2: Happy Holiday Stuff. A weather theme for The Sims 3 was introduced in The Sims 3: Seasons.

Hobby
Sims can pursue their hobbies, so their activities are no longer monotonic, where Sims now have actual preferences over other activities. Hobby enthusiasm is featured in The Sims 2: FreeTime. It also appears in The Sims 4: Get Together.

Social Life
With the addition of reputation and social class, Sims don't just interact with other people and do things unnoticed. What Sims do towards others remains noticed as part of the Social Life theme in The Sims 2: Apartment Life. Social groups, a similar feature, returned in The Sims 3: University Life. Social life was reintroduced in The Sims 4: Get Together.

Luxury
Luxury is a theme based on the stuff appearing in The Sims 2: Glamour Life Stuff, The Sims 2: Mansion and Garden Stuff, The Sims 3: High End Loft Stuff, The Sims 4: Luxury Party Stuff and The Sims 4: Perfect Patio Stuff.

Fashion
Fashion-branded stuff is featured in The Sims 2: H&M Fashion Stuff, The Sims 3: Diesel Stuff and The Sims 2: IKEA Home Stuff

Outdoor
Outdoor is a theme that mostly focuses on outdoor stuff and is appearing in The Sims 2: Mansion & Garden Stuff, The Sims 3: Outdoor Living Stuff, The Sims 3: Town Life Stuff, The Sims 4: Outdoor Retreat', The Sims 4: Perfect Patio Stuff, 'The Sims 4: Romantic Garden Stuff and The Sims 4: Backyard Stuff

Bathroom Style
The enhancement in bathroom design appears in The Sims 2: Kitchen and Bath Interior Design Stuff and The Sims 3: Master Suite Stuff.

Other Themes
Other stuff packs are exclusive to a theme only, which is categorized here.