In which expansion pack were pets first introduced in The Sims series?

In which expansion pack were pets first introduced in The Sims series? The answer is The Sims: Unleashed.

Released in 2002 as the fifth expansion pack for the original The Sims, Unleashed expanded the game beyond ordinary residential neighborhoods with a new community area called Old Town. Its headline feature was the ability to adopt and care for pets, including cats and dogs, making it the first Sims title to introduce household pets as a major gameplay feature.

Players could bring animals home, train them, play with them, and enter pets in shows. The expansion also added gardening and farming-style activities, new objects, careers, and neighborhood features. Pets were not fully controllable in the same way as Sims, which is one reason later pet-focused releases are sometimes remembered as the “first” pet games.

A common mix-up is The Sims 2: Pets, The Sims 3: Pets, or The Sims 4: Cats & Dogs. Those later packs reintroduced or expanded pet ownership for their respective base games, but The Sims: Unleashed was the original series debut.