Theme

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

Family Life
Family Life is the main theme of The Sims: Livin' Large and The Sims 3: Generations. Livin' Large doesn't mainly focus on the interaction between families, but they technically introduce a lot more new features at the time when players are new to the era of The Sims. Meanwhile, Generations mainly focuses on the family, where Sims are meant to "Live the Life to the Fullest". Family time is more elaborated in Generations. The quality time in The Sims 2 is established as stuff from The Sims 2: Family Fun Stuff

Party
Party is the main focus of The Sims: House Party, in which the feature of party was introduced the first time. Party is also more enhanced in Generations, where there are even more types of parties. The Sims 2: Celebration! Stuff provides more party objects for The Sims 2.

Dating
Dating feature 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. Dating feature enables two paired Sims to spend their time together doing romantic activities.

Vacation
Vacation feature is introduced, as the main theme, in The Sims: Vacation, The Sims 2: Bon Voyage, The Sims 3: World Adventures, and The Sims 3: Island Paradise. The main purpose of this theme is to show Sims the other part of the world in their respective games to spend their time and relax while on vacation. World Adventures doesn't mainly focus on relaxation or vacation, but rather exploration and adventuring.

Pet
Pet is the mostly used theme 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 in here. Pets come as the second species players need to tend in addition to the Sims.

Fame
Fame is the main theme in The Sims: Superstar and The Sims 3: Showtime, as well as a part of the themes in The Sims 3: Late Night. Sims are able to work in Fame career, become celebrities, or become performers to pursue their life to become famous.

Magic
Magic appears as the last theme in The Sims: Makin' Magic and The Sims 2: Apartment Life, often interpreted as the last expansion pack to create magical stuff that doesn't make much sense in real life. Sims can become witches to cast spells and do many other magical stuff. Magic is reintroduced in the The Sims 3: Supernatural, via fairies and/or witches and wizards.

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

Nightlife
Nightlife theme is where the game mainly focuses the life at the big town in the clubs, and have outings. There's also the night creature that will make the nightlife more intriguing, vampires. This theme serves as the theme in The Sims 2: Nightlife and The Sims 3: Late Night.

Profession
Sims can run businesses, in addition to going to work in careers, or perform job in their profession. These features enable Sims to earn money not just by simply going to work with adequate skills. Sims can now perform the real work in their profession and business. This theme is mainly in The Sims 2: Open for Business and The Sims 3: Ambitions.

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.

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 other will now remain noticed as part of the Social Life theme in The Sims 2: Apartment Life.

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

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