I want an old Grand Theft Auto style "go around the city causing mayhem," except your characters are a roster of escaped zoo animals.
The objective would be to find a way to get back to your native habitats - by slipping onto a boat or a truck or something - or finding a mate and becoming an invasive species.
You'd be able to swap between, like, a giant anaconda, a zebra, some tropical birds, etc etc. And by causing mayhem in different parts of the city, you could create openings the other animals could take advantage of.