Uhhhhh.... Hmmm... Yes, I'll allow the snake. But no tiny lizards of geckos or anything. If you're gonna be a snake it has to be like... At LEAST rattle snake size. And for the record, no amphibians. I just don't much care for frogs and the like. AND NO FISH. Your animal has to be able to survive on land and/or air, but you can't be a dolphin because that would be utterly inconvenient.

Animals that are okay:

Pretty much all mammals.
Pretty much all birds. No penguins or other flightless birds.
Larger Reptiles. No turtles/tortoises. No little tiny lizards or chameleons/etc.

Animals that are NOT okay:
Fish.
Amphibians.
Insects.
Little teeny tiny animals, excepting mice/rats/etc.