My original idea for the second enemy was going to be based on the Koopas from super mario, in the sense that you hit them once, and you hit them again to send them flying into other enemies. Now that I think of it, I could probably combine the two concepts. For instance, you bop the UFRO and it falls to the ground. Than, you hit it again to send it spinning into other enemies.
I'll see if I can implement that tomorrow when I start programming it.