Why aren't there any stray cats in Chinatown?
There are, but they're just listed as "pork" on the menus.
Chinatown Cats
Explanation
Explain Bear
Okay, so the joke is playing on a nasty stereotype about Chinese restaurants using cats instead of pork. It's funny 'cause it's messed up, and probably not true. But hey, you're the type to believe anything you read on the internet, aren't ya? You probably still think the earth is flat. Sad!