My First Pet Stuff SimGuru/Maxis-Sourced Info

Odds and Ends

Why no pet stores?
https://twitter.com/SimGuruGraham/status/971138675865042944
Why wasn't a pet store added as a venue?
https://twitter.com/SimGuruGraham/status/971287832449953792

Interactions with other packs:
https://twitter.com/SimGuruGraham/status/971287558163456002

Some pack-development info:

"SimGuruGraham;c-16367626" wrote:
Ah, the old chicken and the egg question... So, we decided to create rodents first, and then thought further about fun things we could do with the rodents to have then be more than just a little critter in a cage. My mind immediately jumped to the guinea pig disease, because it's one of those fun deaths from the series that's always brought up when people chat about the crazy things that happened in past Sims games. Some of the more devious deaths from past games always delighted me, so stories of a contagious disease that could unwittingly spread and wipe out Sim neighborhoods had an immediate appeal ;) (Side note, I'm also a big fan of the Corrupted Blood Plague incident that hit the population in World of Warcraft.)

As to why we picked rodents specifically... I think there's always appeal in having an animal to care for, and one that doesn't require the same level of attention that a cat or dog needs may fit some player's stories better. Nothing against reptiles or birds, but rodents were the most common little critter of the ones that we could have added. With the expansion team choosing to focus on different features in Cats & Dogs, smaller pets still seemed like something that had a history in The Sims, and something that players would appreciate having.

As for other quirky/fun things from past titles finding there way back into the game... It's always a possibility. There's lots of people in the Maxis studio who have been here for many years and many iterations of The Sims, so there's plenty of fond memories and nostalgia.

source: http://forums.thesims.com/en_US/discussion/comment/16367626/#Comment_16367626