Leatherhead

Leatherhead is a mutant alligator and an ally to the Turtles. He is voiced by Peter Lurie.

Physical appearance
Leatherhead is an anthropomorphic, 8 ft alligator with a scar on the left side of his chest, green scales, a pale underbelly, and spikes running down his head.

After being stranded in Dimension X for decades, he has aged as he is now gray with more scars.

Early life
Leatherhead started out as a baby alligator and he was raised by a kind, young boy (who's name remains unknown). One day, his parents discovered him and flushed him into the sewers. He was then found by the Kraang, who took him to their dimension and did horrible experiments on him (like exposing him to mutagen). Luckily, Leatherhead could not let them break his spirit. 6 months ago, he escape their dimension and took their power cell so the Kraang will not bring anything from their dimension to Earth.

Season 1
Leatherhead debuted in It Came From The Depths. He retreated to the sewers after he escaped TCRI. Then, some citizens of New York claimed to have spotted him, which makes the Turtles go search for him. When they found him, he was fighting the Kraang, who were trying to get the power cell back. He was then knocked out during the fight, but the Turtles killed off the Kraang. Mikey wanted to help the poor mutant, but the Turltes disagreed with him just because the alligator is supposed to be an aggressive animal. Mikey still wanted to help the mutant, so the Turtles begrudgingly accepted to since Mikey couldn't easily drag the mutant to the lair. When they took Leatherhead to his lair, Mikey shows how kind he is and places his teddy bear. His brothers tried to chain the mutant up, but Mikey refuses to let them. When Leatherhead woke up, Mikey thinks he is calm, but Leatherhead begins to act in a dangerous mode. He rips the teddy bear to shreds and grabs Donnie by the face, much to his dismay. Leo then knocks him back out as Splinter arrives to see the trouble. His sons toled him that Mikey brought a "dangerous monster" to the lair, though Splinter denies them as there is no greater monster than a lack of compassion. They told Splinter that Leatherhead was keeping the power cell from the Kraang. Splinter then discovers Leatherhead's scar, and he reveals Mikey had made a wise decision. He tells Mikey to befriend him when he wakes up, while the other three go search for the power cell before the Kraang can. Donnie asked if they're still chaining him up, and Splinter says, "Of course. I am compassionate, not insane." Later, Leatherhead wakes up, chained to a pillar. Mikey arrives with some refreshments, and the mutant gator glares at him to set him free. When Leatherhead went out of control, Mikey tries to calm him down. He then gives him his world famous pizza noodle soup. When Leatherhead tried it, he said it was the best thing he had ever tasted. Mikey is excited that someone finally likes his cooking. When Mikey asked what was his name, the mutant reveals he does not have one. Mikey then decides to give him a name. He inspects his body parts, then focuses his head, which seems to be leathery. Mikey then gives him the name Leatherhead, much to the mutant's joy. When Mikey asked why he went insane around his brothers and grabbed Donnie's face, Leatherhead reveals there are times when he loses control. When he awakens, he is horrified by what he's done. He says that a monster like him deserves to be chained. Mikey then tells him that he thinks he's a monster because everyone treats him that way, which Leatherhead agrees. Later, Mikey released Leatherhead when his brothers arrived. They were shocked because he might go insane again. When the Turtles show him the power cell, he goes wild and crazy (and grabbing Donnie's face). Splinter arrived and stopped him from harming his sons. Leatherhead is forced to leave with the power cell. Mikey follows him to an old subway train (which would later become the Shellraiser). Mikey tells him how disappointed he is when he trusted him to not act angry. Leatherhead reveals that the Kraang made him this way. After he tells them about his origin, the Kraang have found them and vowed to get the power cell. While Leatherhead holds them off, the Turtles escape with the power cell. Later, two beaten Kraang meet their apparent end as Leatherhead tells them they won't be telling anyone anything. He then lunges an attack on them.

He reappears in TCRI, where the Turtles tried to ask him where the Kraang are located. Once they arrive, Leatherhead, again, goes into rage mode and, yet again, he grabs Donnie's face. Once he snaps out of it, the Turtles told him that they lost the power cell, making Leatherhead angry again before grabbing Donnie's face again. However, Leatherhead controls himself since the Turtles are his friends. He then reveals the only thing he remembered as he makes a familiar symbol on the ground, which Donnie takes a picture of. Later, April sends him and the Turtles to TCRI so they can get the power cell back. While Leatherhead fights some Normans and Mrs. Campbell, the Turtles search for the power cell. Later on, the portal lets Traag from Dimension X to Earth. When Leatherhead arrives, he yells out Traag's name angrily as if they've met before. He then throws a part of the Kraang-droid at the alien golem. He knocks down Traag with his tail and Donnie tells him to get the alien by the portal. Leatherhead throws Traag to the portal as Donnie activates the explosives that are on Traag. The explosives explode as Donnie, Leo, Leatherhead, Raph and Mikey feel like they've triumphed. However, the portal (which is protected by a force field, which they don't apparently see until Showdown). Traag himself is not dead, either. As the portal begins to reopen, Leatherhead pounces on Traag and slashes him. Leatherhead then sacrifices himself to save his friends. He drags himself and Traag back to Dimension X, bidding his friends farewell. Mikey and his brothers are horrified of his loss.

Season 2
In Mazes & Mutants, the Turtles encounter the dragon that resembles Leatherhead, who is apparently holding April captive. Mikey, believing it is his long, lost friend, refuses to fight because of their friendship. However, it turns out that wasn't the real Leatherhead (even Princess April). The Turtles defeat him when they imagined that their weapons are magical. The illusion was seen again when Sir Malachi left.

He makes a return appearance in "Into Dimension X!". He is now seen with gray skin and more scars. He sends a message to the Turtles with a Kraang Communication Orb to tell them that the Kraang have perfected the mutagen. However, he is captured by the Turtles' enemy: the Kraang. Later, the Turtles discover the message he send to them and they head to Dimension X. They later free him and discovered he is now different. He explains that he has aged due to being stranded into Dimension X for decades. Later on, he and the Turtles fight off the Kraang, and they made it back to Earth. Leatherhead and the Turtles prepare to face the next invasion as they give each other a high three.

Trivia

 * When Leatherhead is angry, his eyes are covered with the nictitating membrane, which normal alligators and crocodiles use to protect their eyes when they dive underwater.
 * Leatherhead's head resembles more of a crocodile's than an alligator's.
 * Leatherhead has a scar on the left side of his chest from when he escaped TCRI.
 * A running gag in the series involes Leatherhead grabbing Donnie's face.
 * Every time when he's angry around the Turtles, he tends to grab Donnie's face and shake him like a rag doll.
 * He is a good guy in the series like his 2003 incarnation.
 * One of Leatherhead's movements is doing a death roll, which is an actual movement for alligators and crocodiles when they rip their prey apart.
 * He seems to be resistant to the toxic fumes in Dimension X.