Hypno-Potamus and Warren

Prior to his mutation, which was triggered by an Oozesquito sting[4], Warren was a famous Channel 6 newscaster. He followed the Turtles during their missions, declaring himself as their "greatest foe" despite their lack of awareness of his existence. While the Turtles were attempting to trap Hypno, he trapped Raphael in his "goop trap", which the Turtles found more annoying than frightening. Warren was cut in half by Leonardo after he attacked him and after regenerating his body, he purchased a mystic gemstone that enhanced his physique from Clem's Candy, owned by a cloaked mutant named Clem. He lured the Turtles to a TV studio to attack them, however, he was interrupted by the sudden arrival of Hypno, who cut him in half. He was completely ignored in the resulting fight, but when Hypno was about to kill Michelangelo, Warren intervened, declaring that he would allow no one else to kill the Turtles. In doing so, he sacrificed the gemstone to defeat Hypno and regained his natural appearance.

Warren is self-obsessed and loves receiving attention, seen kissing his own reflection and continually admiring a bust of himself in "Newsworthy". As such, he believes himself to be the Turtles' greatest nemesis and thinks that he is far more intimidating and important than he truly is. Due to the high regard he holds himself in, Warren is easily angered and insulted by others ignoring or demeaning him.

Warren is confident and has a strong will, relentlessly trying to encounter the Turtles to challenge them and going to considerable lengths to save Hypno-Potamus when Baron Draxum holds him hostage. He can be deceptive and callous, lying to and betraying April O'Neil despite her known admiration for him. Warren has a flair for the dramatic shown in the way he speaks, moves, and generally views his life. Without a much desired audience, Warren often monologues to himself and is prone to loneliness

Warren Stone is a mutant earthworm with straight blonde hair styled in a pompadour, red eyes, thick black eyebrows, fuchsia skin with pink and purple stripes, and a diminutive stature. He wears a bright blue single-button blazer.

He was previously a successful stage magician and hypnotist by the name of Mezmer-Ron, who performed magic tricks with a hippopotamus named Doug. During a performance, he was mutated after being stung and injected with ooze by one of Baron Draxum's Oozesquitoes, which the Mad Dogs had accidentally released into the city. Because of the presence of his animal partner, Mezmer-Ron transformed into a humanoid hippopotamus and began stealing the signature animals of fellow stage magicians. The Turtles attempted to capture him using a hippopotamus costume and the scent of a female hippopotamus. Hypno found them just as Warren was trying to entrap and kill them, and attempted to romance a hippopotamus-suited Michelangelo.
When the ruse was revealed, he began battling the Turtles and eventually used his hypnotic powers to mesmerize them. He tried to kill Mikey first but was thwarted by Warren, who used his mystic jewel to reflect the hypnotic power at Hypno. This put Hypno in a trance, effectively causing his defeat.

Hypno is talkative and honest, admitting his genuine feelings on many occasions even to his enemies such as when he states that he cheats on the chore chart of his and Warren Stone's apartment.

Hypno, despite his devious schemes, has been shown to be warmhearted to a degree, happy to witness familial affection between the Turtles. He also has an envious streak, pursuing every successful illusionist out of pure envy since "Newsworthy", or trying to trump his competition (often with very definitive methods).

Mutant
Hypno-Potamus is a mutant hippopotamus with short straight black hair, a black goatee, dark circles under his eyes, red eyes, grey spots on his nose bridge, dark grey skin, and a large figure. He wears his usual outfit pre-mutation with black dress shoes.

Hypno is talkative and honest, admitting his genuine feelings on many occasions even to his enemies such as when he states that he cheats on the chore chart of his and Warren Stone's apartment to the Mad Dogs in "Warren & Hypno, Sitting in a Tree". Warren is self-obsessed and loves receiving attention, seen kissing his own reflection and continuously admiring a bust of himself in "Newsworthy".