In the original Birdman series, he served as a main villian, who used his Mind taking powers to use others to do his bidding.
As seen in Mindless, Mentok has had a very Superman-like origin, including a father who is a green-skinned version of Marlon Brando's Jor-El.
Mentok was sent to Earth as a baby, because his planet was being destroyed. Even as a baby, he had a goatee and large side burns. He blames his mother for wanting him not to be a judge. Just before being shot off to earth, his mother warns him of not joining law. He sees himself as possessing an off the charts IQ, and has attended prestigious galactical schools and yet gets stuck doing petty legal disputes, and is rather sorry for himself.
Mentok is now a court judge who often hears Harvey's cases. He has been given the personality of a cocky and flamboyant stage magician; because of this, he often predicts the result of the cases he presides over before they have even started. He often makes an entrance, such as appearing in a cloud of smoke or from a bolt of lightning. Mentok's gavel is a brain on a handle, which squishes when struck. He also seems to enjoy patronizing people such as Inch High Private Eye and especially the courtroom's bailiff, while the bailiff usually just ignores him and stares forward with a blank expression. His main catch phrase is "Booweeoop" to give the impression of eerie sci-fi theremin music sound and is said whilst moving his hands around in a circular motion often when 'Mind Taking'.
He has various psychic powers including: teleportation, telepathy, hypnotism, the ability to stop time, the ability to literally swap the minds of any creature human or animal, precognition, and telekinesis — all referred to as "mind taking" — but he rarely uses them for anything beyond sophomoric mischief.
In Mufti Trouble Shazzan accuses Mentok of having imprisoned him in the vase centuries ago for gazing on the king's intended. Mentok was a genie called Mufti the Mizwa of Muzzy Tah in those days, one of several identities he has had over the years. Shazzan insists on Peanut representing him, and Mentok, after he is captured, manipulates Harvey into representing him. Mentok insists that Shazzan is attempting to frame him, and escapes from court to retrieve the halves of a magic disk that, when put back together and the magic word thus revealed is spoken (by Avenger), imprisons Shazzan in the vase again.
In Mufti Trouble Avenger asks Mentok to pee in a sample cup for him. The results show he has a low sperm count and dangerously high levels of THC, the main psychoactive chemical present in marijuana.
The production crew of Harvey Birdman once toyed with the idea of Mentok having no genuine powers at all, but the idea ultimately never panned out.
In the episode Guitar Control, Mentok abducts Harvey to help him perform at his nephew's birthday party. Another character of Mentok's race, presumably Mentok's brother, is shown with the supposed nephew. Mentok's brother is chubby and wears casual clothes, while his nephew is dressed in a child-sized version of Mentok's usual outfit.
In the original Birdman cartoon, Mentok's clothes were colored red and dark red. He was recolored to wear black and purple clothes in Harvey Birdman, but his original colors were still showcased during Turner Classic Birdman.
Mentok randomly changes between his original villain costume and a loose-sleeved judge version of the outfit between appearances.