He was the homosexual lover of Herbert Garrison, and his teaching aid before the latter had sex reassignment surgery. Mr. Slave's catchphrase are"Ooh, Jesus Christ!" or "Oh Jesus, Jesus Christ!", delivered in a quavering lisp. He is rarely heard saying anything other than these catchphrases.
His first major role was in "The Death Camp of Tolerance", in which Mr. Garrison, the elementary school teacher of the main characters, learns that he can sue the education board for a lot of money if he is fired for being gay, and does his best to ensure this happens. To this end he hires Mr. Slave as his classroom assistant, or, for short, "teacher's ass". The lessons become increasingly sexual, and degenerate in nature, culminating in Mr. Garrison inserting the class gerbil, Lemmiwinks, into Mr. Slave's rectum.
In "South Park is Gay!" he and Mr. Garrison get annoyed about the Queer Eye for the Straight Guy cast making straight people metrosexual. He, Mr. Garrison, and Kyle Broflovski went to New York to kill them. When they try to turn them into Crab People, the boys' mothers come and kill them.
Despite Mr. Slave's occupation, he is shown to be wise and knowledgeable, offering characters advice when in certain situations. His most prominent moment was in "Stupid Spoiled Whore Video Playset", when he gave Wendy Testaburger advice after she wanted to become a whore after seeing that many of her friends had become part of the new trend. Mr. Slave pushed Wendy to not follow the lifestyle due to his own personal experiences and has claimed to be a whore since the day he was born. As a child he has shown to have faked a fever for his mother to take his temperature through his rear end. In his later life he tried to get other boys involved by pretending to be a voice to shout out to beat up the queer kid where he giggles and says "Jesus Christ" after being tackled by all the football boys. He subsequently competed in a 'Whore-Off' with Paris Hilton, culminating in her being forced up Mr. Slave's ass. However, having finished this, Mr. Slave rejected the applause, telling parents that they had to teach their children that people like Paris Hilton were to be despised or they'd never learn it, prompting the girls to apologize to Wendy.
In the episode "Mr. Garrison's Fancy New Vagina", Mr. Garrison has a sex change operation and becomes a woman. Mr. Slave is upset that he was not consulted on the operation beforehand, which starts an argument, he commented that Garrison never stopped to think how everybody else around her would feel about the sex change, and, being gay, is no longer attracted to Garrison as a woman. When Garrison (now referred to as Mrs. Garrison) callously suggests that Mr. Slave simply stop being gay so that they can continue their affair, he says "How can you say that? You're gay too.", When Garrison responds that she's a woman, not gay, Mr. Slave walks out thus ending their relationship. In the episode "Follow That Egg!", Garrison decides that she wants him back, but learns that she is too late, as Mr. Slave had moved on with Big Gay Al — to whom he is now engaged. Jilted, Ms. Garrison makes an ardent, though ultimately failed, attempt to get gay marriage banned.
Subsequently, Mr. Slave and Al join in marriage. He was seen later making cameos in "The Ring" masturbating in the audience at the Jonas Brothers concert and singing "Queef Free" along with the other guys in "Eat, Pray, Queef". In "The F Word" Mr. Slave and Big Gay Al are the first to see the boys' attempts at getting rid of the local Harley Riders, by writing "Fags Get Out!" Initially they are both pained and horrified by the sign, until realizing that the boys did not mean anything disparaging against gays, but were instead using the term "Fag" in regards to the Harley Riders, stating "You can be gay, and not a fag". Al and Mr. Slave both helped to change the definition of "faggot" from a gay person, to an annoying Harley Rider.
Mr. Slave returns in "Not Funny". The townsfolk are convinced the bombing Denmark is the preventative solution for their internet histories being made public. The town convinces Mr. Slave to call President Garrison and convince him to do so. The two had not spoken since the events of "Follow That Egg!" and Garrison was eager to speak with Mr. Slave. Dismissing Garrison's subtle advances, Mr. Slave intentionally provokes him into attacking Denmark.
- Mr. Slave bears a striking resemblance to the "motorcycle biker" character in the disco group Village People portrayed by Lee Mouton and later Glenn Hughs.
- Prior to "Crème Fraiche", Mr. Slave is the only person in the show to have previously worked at South Park Elementary in earlier seasons and not be deceased. He is still the first known person to survive an employment at South Park Elementary, the others being Randy Marsh, Principal Victoria, and Mr. Garrison.
- When Butters walks into the steam room in "Butters' Very Own Episode", Mr. Slave's voice can be heard. This may or may not be him, for he debuts one year later in "The Death Camp of Tolerance".
- Mr. Slave appears to be a Jonas Brothers fan, as he can be seen at their concert rubbing his groin in the episode "The Ring".
- "Butters' Very Own Episode" - Heard in the background in the steam room.
- "The Death Camp of Tolerance" - Debut appearance. Used as part of Mr Garrisons get rich plan, but the school instead sends The Boys to an Auschwitz like "tolerance camp". At the end he and Mr Garrison are sent to the camp themselves.
- "South Park is Gay!" - Helps Herbert Garrison and Kyle Broflovski kill the "Queer Eye for the Straight Guy". While he and Mr Garrison and Mr Slave are angry about the metrosexuality fad and the robbery of gay culture, Kyle is angry about getting beat up over the fad.
- "Quest for Ratings" - Seen buying cough medicine at the pharmacy with Mr. Garrison.
- "Stupid Spoiled Whore Video Playset" - Wendy Testaburger asks for his help becoming a whore, later prompting him to have a "whore off" with Paris Hilton. Shoves Paris up his ass, similar to how he shoved a gerbil up his ass in an earlier episode.
- "Mr. Garrison's Fancy New Vagina" - Because Mr Slave is gay, he broke up with Mr Garrison for being a "woman" after a cosmetic operation.
- "Follow That Egg!" - Becomes engaged with Big Gay Al and later gets married.
- "The Ring" - Seen briefly at the Jonas Brothers concert, while here he masturbating at the Joan Brothers.
- "The F Word" - Shocked to find "Fags Get Out" on the walls, thinking they were past it.. Then later seen saving the boys along with other homosexuals from the bikers when they changed the definition of fag from an offensive term for a homosexual to a term for a biker or harley rider.
- "Eat, Pray, Queef" - Seen singing the song Queef Free at the end of the episode.
- "201" (cameo)
- "The City Part of Town" - Seen with Big Gay Al holding hands to make the town appear more diverse to the Whole Foods representative.
- "PC Principal Final Justice"- Seen in the crowd of people standing in front of the Whole Foods Market.
- "Not Funny" - Seen convincing his ex-boyfriend, President Garrison, to bomb Denmark.
Mr. Slave makes an appearance in his house, where his package was mixed up with Ms. Cartman's, and Douchebag has to fetch his package from the post office while he gives the package to Liane. After that, he becomes a summon which involves him forcing enemies up his ass. Near the end of the game, it is revealed that the FBI or some other organization stuck a snuke up his ass, and the player must go on a journey inside his ass, where he must battle bacteria, Armed Guards and the Sparrow Prince. Numerous things are found up his ass, like bats, skeletons, dildos and even Mr. Hat.
|style="background: #Template:Color1; color:#FFF; text-shadow:#000 .1em .1em .1em; padding-left:20px; border-radius:5px 5px 0px 0px;" align="center" colspan="2"|South Park Elementary Staff|
|Richard Adler | Ms. Claridge | Mr. Derp | Mr. Garrett | Mr. Mackey | Mr. Meryl | Mrs. Nelson | Mrs. Streibel | Mr. Venezuela | Mr. Wyland | Pearl | Recess Supervisor | Girls' Volleyball Coach | P.C. Principal|
|style="background: #Template:Color1; color:#FFF; text-shadow:#000 .1em .1em .1em; padding-left:20px; border-radius:5px 5px 0px 0px;" align="center" colspan="2"|Former|
|Chef | Mr. Conners | Ms. Choksondik | Ms. Crabtree | Ms. Ellen | Mr. Garrison | Mr. Marsh | Mr. Slave | Ms. Stevenson | Principal Victoria|