The Teenage Mutant Ninja Turtles may have started as a small independent comic book series back in 1984, but they have grown into a multimedia franchise. Started by Peter Laird and Kevin Eastman as more of a parody of other popular comics of the time than anything serious, Turtlemania soon took over when the cartoon series first debuted in 1987. This has led to a wide range of comics published by multiple companies, several television series, many video games and toys, as well as a few movies.

After more than 30 years of adventures, the Teenage Mutant Ninja Turtles have had their fair share of high notes, but they have also experienced some of the darkest times in entertainment. This has caused all four brothers to hide their deepest, darkest secrets. In particular, Donatello has quite a few ugly blemishes in his life as a turtle, depending on which continuity you are referencing. He may be the smart one who “does machines,” but all the brains in the world don’t stop you from getting put through the wringer when you go out and fight crime. Here are Donatello’s darkest secrets that he’d likely want none of us to talk about, if he had a say in it.

15 DONATELLO BECAME A CYBORG

Like everything in the 1990s, the Teenage Mutant Ninja Turtles went extreme when Image Comics decided to publish a new comic when Mirage Studios no longer could. Though the title featured new creators outside of Peter Laird and Kevin Eastman, it took place inside the original continuity and returned the series to black and white.

The series ultimately lasted for 23 issues and was mired in controversy because it physically altered the turtles to a drastic degree. No one was more changed than Donatello, though, who fell out of a helicopter, nearly died, and was transformed into a hulking cyborg with metal limbs and weaponry. It was not something that TMNT fans wanted to see and it was ultimately ignored by a new volume that returned the turtles to normal.

14 DONATELLO WAS BRAINWASHED

Under the continuity published by IDW, an alternate universe storyline was introduced in the one-shot comic Teenage Mutant Ninja Turtles: Deviations. It essentially functioned like one of Marvel’s popular “What If?” comics, where an alternative scenario to a previous storyline is explored. In this issue, the brothers were brainwashed by Shredder and turned evil.

IDW’s TMNT comic previously had a storyline where only Leonardo was brainwashed, but this version of the story had Donatello, Raphael, and Michelangelo also falling under the control of their archnemesis. Splinter is ultimately forced to gather up a new team to fight against his sons, but a lot of people end up dead in the final confrontation. It’s certainly a fiasco that the turtles would not be proud to know they played a part in.

13 DONATELLO KILLED SHREDDER

Few fans of the Teenage Mutant Ninja Turtles know that Peter Laird and Kevin Eastman actually killed off the Shredder in the very first issue. The four brothers fought the Foot Clan on a rooftop and ultimately managed to defeat their enemies. Leonardo may have landed the decisive blow that left Shredder dying, but it was Donatello who brought the fight to a permanent end.

Given the choice to commit seppuku by Leo, Shredder instead decided to take the turtles down with him by unleashing a grenade. Seeing that his brothers were in trouble, Donnie acted quickly, using his bo staff to launch Shredder, and his grenade, off the building. It meant the death of their first enemy and their revenge against the killer of Splinter’s old master.

12 DONATELLO USED A GUN

Karai has been both an enemy and an ally to the Ninja Turtles over the years, and was first introduced in the “City At War” storyline that saw a battle for control of the Foot Clan take over New York City in the wake of Shredder’s demise. The turtles form an uneasy alliance with her in order to stop the war from escalating and allowing Karai to take over control.

In the climactic battle between Karai’s faction and the Shredder Elite, she is nearly killed by one of the ninjas. Left with no other alternative, Donatello grabs a nearby gun and uses it to kill the attacker. He may have saved a life, but it left him feeling disgraced, having gone against everything he was taught about honor. He soon leaves his brothers to reflect on this great shame.

11 DONATELLO LOVES APRIL

Donatello and April have always had a close relationship, but it is in the 2012 animated series that Donnie actually has strong romantic feelings for her. Considering he is a mutant turtle and she is a human girl, it was probably never going to work out, but that didn’t stop Donatello from trying to win her heart. Over the course of the series we see the ups and down between them.

When Casey Jones shows that he has a thing for April, Donatello becomes paranoid and competitive for her. For a long time he has kept to a secret from everyone else, though Raphael, and even April at one point, seem to know the truth. It isn’t until Donatello confesses to her and is ready to move on that she surprises him with a kiss.

10 DONATELLO DIED (NEARLY)

At one point in IDW’s run on the Teenage Mutant Ninja Turtles, Donatello went through quite the ordeal when he nearly died. Bebop and Rocksteady ganged up on him, beat him half to death, and broke his shell. It looked very likely that for the first time ever, one of the brothers was destined to die. Thankfully, he was able to be saved, but it took quite some time to get him right.

The turtles saved their brother’s body while his soul was transferred into the body of Metalhead. That’s where he lived for some time while his body was recuperating from the attack. Once his body was healed, his soul was transferred back and everything turned out well for him. It was quite the dark time for Donatello and the turtles.

9 DONATELLO WAS BATMAN

Back in 1993, Donatello had a pretty bad day on the Teenage Mutant Ninja Turtles animated series when he transformed into a violent vigilante in the episode “Night of the Dark Turtle.” During a fight with Shredder, Donnie ends up getting electrocuted and falls unconscious, only to wake up with a deeper voice and a much more aggressive and angry disposition.

Seeking revenge against Shredder for everything he has done to the turtles, Donatello puts together something of a superhero costume and starts calling himself the Dark Turtle. As the new Batman of New York City, Donnie goes about fighting crime and hunting down Shredder. More violent than ever before, he nearly kills him, before he is electrocuted again and turns back to normal.

8 DONATELLO WAS SHRUNKEN

In Volume 4 of Mirage’s run on the Teenage Mutant Ninja Turtles, the continuity of the original series is picked up again. In this run, Donatello ended up getting shrunken down to the size of an action figure by a group of Utroms. Unfortunately, due to his mutation, the aliens were not able to find a way to restore him to his original size, so he remained stuck like that.

Ever the positive thinker, Donnie used his small stature to his advantage to go places the enemy would never allow him if he were normal sized. As the smart one, Donatello was also able to create a robotic body that looked like a turtle in order to house his tiny turtle body inside. Just like in the Image Comics run, Donnie was relegated to live inside the inner workings of a machine.

7 DONATELLO CREATED A VILLAIN

When Archie Comics published a run of turtle comics called Teenage Mutant Ninja Turtles Adventures, a storyline introduced future versions of the brothers. In this reality, Donatello sold his inventions and become insanely rich. He also built mechanical armor for all four brothers to wear in battle, which tied into an action figure line. Donnie also did something pretty unspeakable, though no one outwardly discussed it.

Donatello had a lab assistant named Manx, who was a mutant anthropomorphic cat. Ever the tinkerer, Donnie altered Manx’s body to add cybernetic implants, which eventually drove the cat insane and become the villain known as Verminator-X. Manx was eventually restored to his normal self by the end of the storyline, but how exactly do you forgive someone for altering your body like that?

6 DONATELLO BECAME A MONSTER

The 2003 incarnation of the Teenage Mutant Ninja Turtles animated series has a bit of a monster problem. In the show’s third season, the turtles are forced to deal with a monster outbreak, but things go a little nuts when it turns out that Donatello is actually one of them. Now a monstrous and violent version of his former self, Donnie is a danger to his brothers and allies.

After he nearly kills Casey Jones, the turtles are able to capture their brother, but curing him of his ailment is no small thing. The group demands that Baxter Stockman, who is responsible for the monster DNA that infected Donnie, cure their brother. It takes several episodes to return him back to normal, and once he’s cured he doesn’t remember any of it. That’s probably for the best, considering everything he did.

5 DONATELLO ADDED A BLADE TO HIS BO

In the 2012 Teenage Mutant Ninja Turtles, Donatello takes some issue with his dedicated weapon. Typically seen wielding his trademark bo staff with ease, this version of the character is unhappy with the weakness of his weapon, having seen it broken far too often. He managed to modify his weapon by inserting an extendable blade on the end of it, transforming his bo into a naginata.

It’s hard to see Splinter being ok with this change, considering Donatello was trained in the art of bojutsu, and introducing a blade to his weapon would require him to learn a completely different form of fighting called naginatajutsu. Furthermore, while the bo was a weapon of self defense used by farmers, the naginata is an offensive weapon used by samurai. This seemingly simple addition was really anything but.

4 DONATELLO’S ROBOT LOST ITS MIND

When Donatello was nearly killed, the Metalhead body that housed his mind retained a digital copy of himself. This new Metal-Don had all the memories and personality of his real-life counterpart, but his existence as a robotic copy deeply disturbed him, and the memories of the night where he nearly died cause him to lose what is left of his mind.

Metal-Don becomes increasingly distraught at his situation, and even attempts to take Donatello’s body for himself. The conflict between his emotions and robotic body come to a head when he uploads a virus that destroys his sense of empathy and emotion, leaving him as the cold and calculating machine that he feels he has already become. The whole story was deeply disturbing for Donnie.

3 DONATELLO WENT TO REHAB

Former child actor Corey Feldman famously voiced Donatello for the first live Teenage Mutant Ninja Turtles movie in 1990. He had made a name for himself in the 1980s by appearing in films like Friday the 13th: The Final Chapter, Gremlins, The Goonies, Stand By Me, and The Lost Boys. However, like many child stars from that time, Feldman struggled with drug abuse.

Following his turn as a turtle, Feldman decided to get help with his addiction and was in rehab when Teenage Mutant Ninja Turtles II: The Secret of the Ooze went into production. He was replaced for the sequel but managed to return to the character for the 1993 Teenage Mutant Ninja Turtles III: Turtles In Time. It was a dark chapter in the history of Donatello that ended on a positive note.

2 DONATELLO CAUSED A POWER STRUGGLE

We all know that Leonardo is the leader of the turtles, but did you know that Donatello is usually considered to be the second in command? It would appear that his brains make him a pretty good leader when the need arises. While Leo and Raphael usually fight over who is leading the team, it’s always been Donnie who takes over when leadership is in question.

This came up in 2007’s TMNT animated film when Leonardo leaves the group to find himself. Splinter names Donatello as the new leader of the group, which causes Raphael to leave in anger. He already thinks he should be leader when Leo is around, so he was definitely not happy that he wouldn’t be leader when the opportunity came up.

1 DONATELLO ABANDONED HIS BROTHERS

In the IDW miniseries Turtles in Time, the four brothers travel to a futuristic New York City where they find Shredder and Krang as word conquerors. While hiding out in the sewers, they come across an older Donatello, who is the last survivor of the turtles. It turns out that Donnie had given up the fight against evil, though his brothers went on to fight and die against their enemies.

The idea that Donnie would abandon his brothers made the younger version sick to his stomach. Through the actions of the younger turtles, the older Donatello rediscovers his spark for fighting and joins the resistance. However, it cannot be forgotten that he once abandoned his brothers to die. He’ll likely live with that shame for the rest of his life.