Hypno was originally a successful stage magician named Mezmer-Ron who performed alongside his pet hippo Doug. During on a performance he was mutated due to Baron Draxum's Qozeuitoes and because of his animal partner into a hippo renaming himself Hypno-Potamus. He had since turn into a villain. He First appeared in the Episode Newsworthy alongside another villain named Warren Stone. The Turtles had Raph and Mikey disguise themselves as a female hippo to draw him out. He is defeated by Warren Stone.
Hypno returns in the episode Hypno! Part Deux where he watched a teenager made a middle school disappear. An envious and enraged Hypno decides to make a high school disappear and said high-school was April's and he used his powers to brainwash the school so that he would make the school disappear. Eventually Leo and Raph show up to stop him and foiled his plans at the end.
Hypno later reappears in the episode Stuck on You, where he breaks in the museum in order to use a tomb to resurrect his partner Doug who he still misses and had disappears. The Turtles manages to stop him.
In the Evil League of Mutants, Hypno-Potamus joined forces with Baron Draxum, Meat Sweats, Repo Mantis, Warren Stone, and the Sando Brothers to destroy Ninja Turtles after having coffee alone. After tricking the turtles to an abandoned warehouse, the league ambushed them and nearly defeated them, but they used their training to defeat the group.
In Warren and Hypno, Sitting in a Tree, he lives in an apartment with is love interest Warren Stone.
Powers and Abilities
Hypno as a mutant gained the ability to use his voice to brainwash others and using cellphones as well. He is also capable of using other powers like his hat and other gadgets.
Hypno-Potamus has shown a romantic interest in both men and women (meaning he's bisexual).
In "Newsworthy", after falling for a hippo, unaware that it's really Mikey in disguise, he calls "her", "future Mrs. Hypno-Potamus".
"Warren and Hypno, Sitting in a Tree" reveals that Hypno and Warren Stone have developed romantic feelings for each other since becoming roommates.