Leatherhead

Leatherhead is a mutated crocodilian from the Teenage Mutant Ninja Turtles media.

He is a scientist animal that was mutated from mutation that makes him very smart into a humanoid crocodile.

He was recruited by the Utroms, his adoptive family that uses the DNA mutation to make him smart. He began to hate Baxter who works for Shreeder who was the worst enemy of the Utroms to seek revenge against him for betrayal.

He was witnessed that Donatello was mutated into an dangerous reptillian monster that rampages everything. Leatherhead, Baxter and the Turtles work together to return Donatello back to his normal self.

In 2012, he was a normal pet crocodile bought by a young human boy. When the boy's parents found out, they flushed the crocodile down the toilet and it got captured and mutated by the Kraang. The Kraang were unable to turn him evil, though. He stole a device that powered the Kraang's portals and escaped, eventually befriending the Turtles thanks to Michelangelo. He is seen helping the Turtles against the Kraang, he has scars on his body and he hates the Kraang, as he flies into a rage nearly everytime someone mentions them.

He serves as an anti-heroic protagonist in the cartoons.

Leatherhead was originally recruited by Shreeder, but in 2003 and 2012-present, he serves as one of the protagonists in all of the appearences of the shows.

In Cartoons
In the 2003 and 2012 versions (Except 80s version), he mostly serves as an ally to the turtles.