Well, you're not the
first, so much I can say
Well!
I wanted to give small "gifts" (in form of a reference or a cameo or soemthing) to certain people, an idea that came around the xmas holidays, rather then interrupting the work on the flash to do several thingies seperatelly.
I didn't get any better idea for a Danbuster reference that wasn't completely out of the movie's context
so after some consideration, the only thing that came to my mind was placed in the bonus section instead
Yeah, came up with that since Cream the Rabbit is ... uh ... a rabbit as well, and in Sonic Advance 2, her debut game, she can curl up into a ball too.