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The Warden (voiced by David Wain) is the proprietor and warden of Superjail and main protagonist of the series. He is a tall, thin man clad in a purple tailcoat and top hat, gray gloves, pink cummerbund, and round yellow-tinted glasses. The Warden has been described as a "sadistic version of both the Mad Hatter from Alice in Wonderland and Willy Wonka from Charlie and the Chocolate Factory". Despite having an ever-cheerful and friendly disposition, he is actually a severely deranged and violent sociopath due to his upbringing by his cruel father. The Warden devised Superjail as a means for expressing himself and regularly endangers the inhabitants of Superjail, often intentionally, to satisfy his whims. He has very little respect for human life, and one day wishes to incarcerate all of humanity within Superjail, according to one episode depicting an alternate future where he conquers the entire world and transforms it into a single prison state. Rather than handling any actual administrative tasks, he spends most of his time lusting after Chief Guard Alice or indulging in his own bizarre fantasies. The Warden also possesses magical abilities, like the ability to shapeshift into virtually anything he can imagine, and controlling the laws of reality within Superjail. Though the Warden's name is never revealed, David Wain answered "Mark Davis" in a Reddit AMA. In an interview with FreakSugar, Karacas revealed that the Warden is romantic asexual, although he is frequently depicted expressing explicitly sexual interest in Alice.
Jared (voiced by Teddy Cohn) is Superjail's large-headed, long-moustached, uptight/high-strung accountant and the Warden's primary assistant. Jared handles most of Superjail's administrative duties and extracurricular activities, like the Superjail Newspaper. He was first brought to Superjail as a prisoner for unknowingly working for the mafia and got his current job when he impressed the Warden with his intelligence and financial skills (An allusion to The Shawshank Redemption). He is in recovery for, according to the creators, every addiction possible: alcoholism, drug addiction, gambling, and compulsive eating.
Alice (voiced by Christy Karacas) is Superjail's head prison guard. Alice regularly engages in sadomasochistic rituals with the prisoners (often without their consent), all the while rebuffing the Warden's advances. Originally a male guard at a normal prison, she discovered her true nature after falling in love with that prison's homosexual warden, who quickly fired her as a result of his transphobia. Alice was hired by the Warden shortly thereafter.
Jailbot is a white, tombstone-shaped, levitating robot that the Warden created to perform tasks in and around Superjail. Within his simplistic-looking body seems to be a limitless storage space, from which he can produce a vast arsenal of deadly weaponry and tools, including numerous telescoping arms. He is mute, with a dot matrix screen that displays a simple expressive face. Despite his ruthlessness, Jailbot also possesses a childlike personality, protecting the Warden from any harm and watching out for the welfare of children. Christy Karacas described him as a "red-headed stepchild...seeking approval".
The Doctor (voiced by Christopher McCulloch) is the resident physician of Superjail. He regularly experiments on the inmates in gruesome ways and has a German accent, but at times says words in French. It was revealed in "Vacation" that he fought in World War II and was a POW.
The Twins (both voiced by Richard Mather) are identical twin aliens with European-sounding accents who inhabit a laboratory underneath Superjail. They took a year abroad trip to Earth and then decided to stay, much to their father's dismay. The Twins use their alien powers—including teleportation, shrinking, and materializing various items to interfere with the Warden's plans for their amusement.
Jackknife (voiced by Christy Karacas) – A low-level criminal who communicates only by way of grunts and shrieks. He is labelled by Jared to be Superjail's most vile inmate due to his upbringing and near lack of any form of morality. Jackknife is depicted as being short-tempered, violent, and misogynistic. He escapes often from the jail and is brought back by Jailbot during each opening sequence. In "Oedipus Mess", Jacknife is revealed to have sired a son with one of Ultra-Prison's inmates. Having recognized the child as his, Jacknife escaped while the Warden created 10,000 clones of Jacknife who ran amok worldwide until they were killed.
Lord Stingray (voiced by Eric Bauza) is a stereotypical supervillain character, akin to Cobra Commander, and is one of the main antagonist of the show. After being defeated by his army-themed enemies, he crash-landed on Superjail Island and tried to take it over, but ended up getting imprisoned. He has been a thorn in the Warden's side ever since by trying to either escape or take over Superjail.
