Fosse McDonald is a student at South Park Elementary who was often seen in the early seasons with Bill Allen. Similar to Beavis and Butthead, Fosse often calls things "gay" followed by laughing in a deep voice.
Fosse wears a purple shirt similar to Terrance Mephesto's, except with many more stripes along with black suspenders. He also wears black pants and matching gloves. His hair is black but stringy, meaning it could be a different color if it was full. He had thick eyebrows during the first four seasons, but was later redesigned to have regular ones.
Fosse is a bully, often laughing at things and people (in a similar matter as Beavis and Butthead). In addition, he thinks everything is gay; on one occasion Fosse even said "we're gay", which shows his apparent opinions on everything. Due to his seeming stupidity, it appears he did not make it to the fourth grade - he is never seen in the fourth grade classroom, but is in the halls, and is only seen in the hallway and playground after the second season. His voice appears to sound almost the same as Bill Allen's. He was seen in "Lil' Crime Stoppers" when the boys discovered he, along with Bill, had stolen Sarah Peterson's doll. They then played along and were "shot" in the game; however, they were just playing a game and didn't die. Fosse seems to be one of the more naive children in the school along with Bill, Butters Stotch, Jason, and DogPoo. In the episode "It's a Jersey Thing", he is seen as part of Cartman's group to help capture and lock up Kyle. It seems that unlike most other kids, (Craig, Token, Jimmy Valmer) who are more aware of Cartman's manipulating methods, Fosse still hasn't wised up to it and so that is why Cartman would most likely seek him out for help.
Due to Fosse's quick phasing out from the series, his family was never officially seen. In the episode "Damien", two older men are seen in the bar after Jesus storms out, saying "This show's gay" followed by "Yeah, gay" in the similar style to Bill and Fosse, while also having the same face and clothes but adult bodies. In the commentary of the episode it was revealed that these two characters were indeed Bill and Fosse's parents.
- Fosse was a part of Cartman's entourage to eliminate Kyle in "It's a Jersey Thing". Although he doesn't speak, it's arguably his first major appearance since "Lil' Crime Stoppers".
- Bill and Fosse are referred to by Matt and Trey within the scripts and commentaries as 'the Nerds', 'the Bullies' and the 'That's Gay Kids' - they actually rarely use the duo's real names.
- Outside of "An Elephant Makes Love to a Pig" Fosse is never seen in the classroom seats at the same time as Bill - Bill is often there into the third season, and Fosse would occasionally reappear. Bill once appeared in 4th Grade Classroom B, but Fosse did not appear with him.
- Fosse's original voice had a different pitch in the first season. In the second, third and seventh seasons, his voice is much deeper and sounds almost identical to Bill's. He also has a deep voice akin to Bill's in "An Elephant Makes Love to a Pig", though in his preceding and immediate next appearances it is at its original pitch.
- In "T.M.I.", his name is revealed on the chart as Fosse McDonald.
- Fosse's hair looks similar to the Charlie Brown character Pig Pen's hair.
- "Big Gay Al's Big Gay Boat Ride" - He and Bill mock Stan's dog Sparky for being a homosexual.
- "An Elephant Makes Love to a Pig"
- "Pinkeye" - Seen dressed as a Chewbacca.
- "Mr. Hankey, the Christmas Poo" - Participates in the Christmas play.
- "Summer Sucks" - Plays the tuba in the school band.
- "Clubhouses" - Passes Bebe's note with Butters and Kevin up to Stan.
- "Tweek vs. Craig" - Watches Tweek and Craig fight.
- "Hooked on Monkey Fonics" - Seen at the dance.
- South Park: Bigger, Longer & Uncut (Cameo)
- "Timmy 2000" - Seen in the audience for Timmy and the Lords of the Underworld.
- "Proper Condom Use" - Seen in the cafeteria.
- "Professor Chaos" (Cameo) - Seen as a candidate for as a new friend Stan Marsh, Kyle Broflovski, and Eric Cartman, but does not get picked.
- "Red Hot Catholic Love" (Cameo) - Seen watching Cartman trying crap out his mouth.
- "Bebe's Boobs Destroy Society" - Seen in the cafeteria.
- "Lil' Crime Stoppers" - He along with Bill are revealed to have stolen Sarah Peterson doll.
- "Le Petit Tourette"
- "Butt Out" - Seen running out of the burning school.
- "Raisins" (Cameo) - Seen playing Football.
- "Douche and Turd" (Cameo)
- "Quest for Ratings"
- "Best Friends Forever"
- "Smug Alert!" - Seen at Cartman's party.
- "Tonsil Trouble" (Cameo)
- "The List" (Cameo)
- "Breast Cancer Show Ever" (Cameo) - Seen watching Cartman and Wendy fight.
- "Elementary School Musical" (Cameo)
- "It's a Jersey Thing" - Seen as part of Cartman’s group to capture and lock up Kyle.
- "Crème Fraiche" - Seen in the cafeteria.
- "Funnybot" (Cameo)
- "T.M.I." (Cameo) - Seen checking the length of his penis.
- "1%" - Seen in the fitness class
- "Faith Hilling" - Seen in the memeing class with the other 4th Grade students.
- "Jewpacabra" - Seen at the Easter egg hunt.
- "Butterballs" - Seen in Stan's anti-bullying video.
- "Cartman Finds Love" - Seen in the background on the playground.
- "Going Native" - Seen eating in the cafeteria.
- "Let Go, Let Gov" - Seen eating in the cafeteria.
- "Black Friday" - Joins the PS4 army.
- "A Song of Ass and Fire - Seen as a member of the group that wants to get PS4s on Black Friday.
- "Stunning and Brave" (Cameo) - Seen at the studen/parent/teacher assesbly.
- "The City Part of Town" - In the choir of children welcoming the Whole Foods inspector
- "Wieners Out" - Seen in the school cafeteria.
- "Douche and a Danish" - Seen making danishes in the school cafeteria.
- "SUPER HARD PCness" (Cameo) - Seen in the gym after evacuation.
Fosse is a minor character in the game. He participates in the attack on South Park Elementary and Clyde's fortress alongside the player. He is seen being attacked by three elves, and he befriends the player after he saves them.
Fosse can be found with Bill at the Raisins bar. When interacted with, Fosse says, "Sorry, you're not my type" with regards to the player, Bill then responds with, "Yeah, he's taken", referring to Fosse. This is confirmation that Bill and Fosse are, somewhat ironically, in a relationship with one another.