Alim Coelacanth (nicknamed Merdude by Michelangelo) is a man/fish-like creature from the lost city of Atlantis, and is also its true ruler. Merdude left Atlantis over 200 years ago in search of others of his kind - it seems that Merdude is the only mutant in the lost city.
By the time Alim and the Turtles arrive, Bebop had been crowned king and issued the order to "clap them in irons." However, Alim and the Turtles disappeared back into the sewers beneath the city of Atlantis. Confused, the Turtles ask Alim why none of the Atlanteans seem to recognize him, and he explains he left Atlantis a long time before any of them were even born.
After showing the Star of Atlantis to the Turtles, he encounters the imprisoned Hepax Lagamina who tells him he is the true king of Atlantis and convinces Alim to challenge Bebop to single combat in the Atlantean arena. Atlantean guards arrive and chase him and the Turtles though the sewers. Alim uses his telepathic powers to call upon his friends of the deep who stop them.
Alim challenges Bebop to combat, despite his own limited combat skills. In the arena Bebop gains the upper hand, as he unfairly uses his laser gun (and Alim cannot move around well on land due to his lack of legs), and Alim is on the verge of losing until Hepax arrives and tells him to use the Trident of Power. With a cartwheel and a slap to Bebop's face with his tail, Merdude manages to reach and wields the Trident of Power. Bebop quickly renounces his throne.
He chases after Shredder who stole the Star of Atlantis. Shredder blasts a hole in the city's dome, threatening to flood the city. However, Alim summons a giant squid to seal it. Subsequently, he and the Turtles reclaimed the Star of Atlantis from the Technodrome and returned it to Atlantis. He was crowned king, and immediately named the young and beautiful Atlantean Hepax Lagamina as his royal counselor.
Shredder launches a counter attack with the Technodrome but Alim stops him with the Hammer of Atlantis which damages the Technodrome and forces Shredder to retreat. As a final thanks to the Turtles who helped him, he summons four giant sea turtles to escort them back home.
- While "Merdude" was a prehistoric boy mutated into a merman in the Archie Comics, this incarnation made him a deformed Atlantean (he had always resembled a fish-man).
- Alim lacks the eye-patch of the original Archie Comics and action figure version.
- His last name comics from Coelacanth, the species of fish of which he is related.
- He is similar to the DC Comics character Aquaman as both of them are kings of Atlantis that have mental powers over sea life.