I always wanted to have a seven eyed cat. A four on the head (front and back) one on each hip, and one on the end of it's tail.
I had limited success (around %30) with taking plugs of tadpole flesh and implanting them into pre-adult frogs (legs, still a tail) just under the skin. I found it was fairly easy to get another leg to start, but eyes and more complex features didn't take. Still, there was something gratifying about having freak frogs for my eighth grade biology project.
But that aint gentics, that's just sick.