Hey guys. I see a few of you are concerned/confused about what to do. My advice would be to start out thinking about the coolest looking designs possible. Often times it's easy to get locked up thinking about how exactly something works. Don't paralyze yourself by trying to make it too logical. Remember, it only has to LOOK like it works! Also, I don't have a problem with slightly oversized characters, or characters who don't "act like they're supposed to." Just look at games and film. There are plenty of examples of anthropomorphized animals that do not adhere specifically to the rules of their species. Woody Woodpecker, Chester Cheeta, Yoshi, Kung Fu Panda--the list goes on. Feel free to push the boundaries of what's possible!
Don't forget that it has to have the illusion of functionality, but we are not, for the most part, mechanics or engineers. Try to strike a good balance between reality and fantasy.