Anything that can happen, given enough time and opportunity, will happen.
I could imagine a zoo of DNA manipulated animals, and it getting out of control as they keep going for scarier and more impressive. I could imagine people wanting some cat attributes in a dog, etc, leading to designer animals.
Maybe like a dog-gerbil? A dog that can exercise itself on a wheel. etc (my attempt at humor)
Dog wheels were actually used at one time to power small hand or foot powered farm equipment that had been converted to run on a pulley system with a power source.
The dog wheel was used as the power source instead of an engine or motor.
Might still be used in some places without any other power source.