Leatherhead is a fictional character in the Teenage Mutant Ninja Turtles (TMNT) comics and all related media.

The character first appeared in Tales of the Teenage Mutant Ninja Turtles #6 (August 1988) and was created by Ryan Brown.

The now-homeless Leatherhead was forced to live in the sewers where he was continually attacked by a big-game hunter called Jack Marlin.

It is unknown what his current relationship with the Turtles is, but Raphael's comment that he hopes that he did not hurt Leatherhead would make it seem as if they are at least on good terms.

It is revealed that the Illuminated were secretly drugging Leatherhead, which caused him to subconsciously build the second Transmat Device that he was working on in issue #8, then wake up and remember little.

In the past, at several comic conventions, Leatherhead creator Ryan Brown has said that he initially intended to kill the character off at the end of Tales of the Teenage Mutant Ninja Turtles vol.

Before he could free Leatherhead, Leonardo was attacked by King Komodo and his monitor lizard minions, the actual killers of the children.

He started off as a giant alligator until he swam through a mutagen-polluted (thanks to a previous botched mission by Krang and Shredder, the one that gave birth to the Punk Frogs) part of the swamp, where he mutated to his current humanoid form.

In one episode called "Night of the Rogues", Shredder hired him and the Rat King, along with Slash, Tempestra, Antrax, Scumbug, and Chrome Dome, to help him and Krang destroy the Turtles.

Original creator Ryan Brown went back and redesigned his Leatherhead character for this particular incarnation of the Ninja Turtles.

[2] In the Archie TMNT Adventures Comics, Leatherhead starts as a poor human named Jess Harley who lived in the swamps of Florida, and became transformed into a mutant alligator when the "witch" Mary Bones (actually the former warlord Cherubae from Dimension X in disguise) used the Turnstone on him.

In his desperation to return to his family, he befriended Baxter Stockman and helped him create a new body, while working on a transmat device so that he could rejoin the Utroms.

The resulting battle caused a cave-in, and despite Michelangelo's pleas for him to follow them, Leatherhead seemingly gave his life for his new friends.

Leatherhead later reappeared, surviving because of his tough skin, as a prisoner and object of experimentation in the lab of Agent Bishop.

Leaving the Turtles, a depressed Leatherhead found himself hunted by an extreme game hunter, Mr. Marlin, through the sewers.

He is later revealed to have helped Donatello create the Monster Hunter gear used by the Turtles against Bishop's mutant creatures.

Reminded of the trauma he had suffered, he was tempted to exact revenge on Bishop, but managed to control his anger with the help of his friends.

After suffering long and brutal torture, Leatherhead escaped back through the portal that connected Earth to Dimension X with a piece of the Kraang power cell.

During his absence, an illusion of Leatherhead is conjured by Sir Malachi during "Mazes and Mutants", played up as the typical fairy-tale dragon for the Turtles to defeat.

Together, they stymie the forthcoming Kraang invasion of New York, and though Leatherhead once again tries to sacrifice himself to save the Turtles, Mikey is able to bring him back home to Earth.

Half a season later, Leatherhead returns as the second-in-command of the Mighty Mutanimals, a ragtag group of mutants formed by Slash that have been fighting the Kraang invasion since the taking of New York.

Leatherhead is overjoyed to be reunited with his friends, especially Michelangelo, and takes part in the battle to evict the Kraang from New York.

In "Clash of the Mutanimals", Leatherhead and Pigeon Pete work to free their brainwashed comrades Raphael, Slash, and Rockwell when the Shredder uses them as test subjects for a mind control serum.

In the third-season finale "Annihilation: Earth", Leatherhead nearly attacks Bishop, a defected Kraang, and does not come to trust him until after they work together to take down the Technodrome.

When Splinter fell in battle against the Shredder, Leatherhead and the other Mutanimals attended his funeral in the fourth season finale "Owari".

In The Big Blowout, Leatherhead and the other Mutanimals team up with the Turtles, their 1987 counterparts, April, Casey, Karai and Shinigami to defeat Bebop and Rocksteady, who are recruited by Krang and the 1987 Shredder.

Leatherhead has also made an appearance as a boss in Teenage Mutant Ninja Turtles 2: Battle Nexus, although the cutscene shows him as an ally.

Leatherhead does appear in the DS version of the game as a boss fight and in a level or two where he teams up with the Teenage Mutant Ninja Turtles.

Leatherhead appears as a boss in the 2022 beat-'em-up Teenage Mutant Ninja Turtles: Shredder's Revenge.