When i was younger i remember playing a Nes game were you were this guy who could transform into animals like a lion, an eagle and other animals. I also remember the second level (or one of the other early stages) to be at the circus. Does this sound familiar to anyone?

Grtz, Henk

Closest thing I can remember is Ninja Crusaders. You could turn into a tiger, falcon, scorpion, and a dragon based on the weapon you had. Don't recall a circus, another possibility is Circus Charlie. You rode animals during levels like a lion and a horse, also jump monkeys and ride beach balls lol.