It's more fun if animal forms give abilities related to the animals the forms are based on, but let's face it: animals move the way they do because of how their bodies are shaped, and it's not just one or two characteristics. It's the whole of the body.
Of course, this strip takes unreasonable expectations to an extreme, but I think Tedd forgot to factor in Grace's natural bounciness.
My favorite "ah, no" super hero to point out is Spider-Man. Spiders, along with other small creatures, can do what they do because of their tiny size. It makes even less sense than most animal-based heroes for him to get his powers from a spider. It would actually make more sense to me if he got his powers some other way and just decided to be "Spider-Man" due to the similarities (particularly in continuity where his webbing is genetic).
Then again, now I'm trying to bring logic into Spider-Man, and that can never end well.
Tags: Grace, Tedd, tf, bunny!