Well there are the mutations to experiment with:
You can mutate all the way through the chain 17 different things I believe... getting hit as the Big Tomato will turn you into the baby, which mutates much further down the chain to winged tomato... then there is the fish, which if hit becomes lobster... there are a lot of things to try and turn into, that is one very fun thing to do in the game. I think it is a very refreshing shooter, a bit short, but a lot of fun to pull out once in a while.
-Nick