Teenage Mutant Ninja Turtles, Season 4

Leatherhead:
(Narrating) As we fly through the night, I can't help but ponder: intelligence, reason, even simple thought. Most people take these things for granted. I do not. For I know what it's like to be an advanced mind, trapped in the body of a brute... of a monster. But for once, I am not the monster in question. My friend Donatello is one of the gentlest souls I've ever met, with one of the finest minds I've ever known. But now, thanks to the evil agent Bishop, my friend has been transformed into a thoughtless savage. And I fear that the Donatello I know may truly be lost forever.