One of the most interesting picture tricks ever devised (Guy Wright is brilliant), but also one of the most difficult to perform so that you can easily tell what it is. If you are able to get it, though, it's a really fun one to do for small audiences.
The trick to making the bunny proportioned correctly is making the structure on your throwhand as large as possible, especially as you're wrapping it onto the yoyo. From there, you have more freedom to adjust the structure just right. Otherwise, the ears will be freakishly huge, and nobody wants freakishly huge ears.