Brimmy is a 4th grader at South Park Elementary. He has remained a background character since the first season and still appears often in the show. Naturally, as a background character, he is mute, and seldom speaks. He was also left unnamed, generally referred to by the conjectural title, "boy with blue cap", until his name was ultimately revealed to be Brimmy in the South Park video game, South Park: The Fractured But Whole. Despite being a background character, he also has an "advertisement" for the FAQ on South Park Studios.
Despite having been the boys' classmate since 3rd grade, the closest time of his voice being heard was a short grunt of pain after being hit by a dodgeball in "Conjoined Fetus Lady". He can be seen yelling "Yeah!" in "Quest for Ratings", however, his voice is lost among the crowd. He appears as a background character numerous times throughout the show, especially in hallway scenes and on the playground.
- Assault and Battery: He is seen beating up one of the mall employees with a Mr. Hankey toy in "Merry Christmas Charlie Manson!"
- Civil Unrest/Rioting: Participant in the riot of children at the Nebraska mall in "Merry Christmas Charlie Manson!"
- Arson: Throws a lit Molotov cocktail at the Lollyland stepup in the Nebraska mall in "Merry Christmas Charlie Manson!".
- Graffiti: Spray paints the walls of the Nebraska mall in "Merry Christmas Charlie Manson!".
- Shoplifting/Breaking and Entering: In "Merry Christmas Charlie Manson!", he, along with two other kids, throws a bench at the window of an electronics store in the mall, and steals the store's items without paying for them.
- Indecent Exposure: Participant in the "Wieners Out" movement formed by Butters Stotch, which involves boys walking down the hallway of South Park Elementary showing their genitalia.
Brimmy wears clothes that are very similar to Craig's usual garb, he wears grey trousers, a blue coat and a blue cap with a yellow brim. Several other unnamed background characters can be seen with similar appearances to Brimmy, having different colored clothes.
- "Mr. Hankey, the Christmas Poo"
- "Tom's Rhinoplasty"
- "Conjoined Fetus Lady"
- "Summer Sucks"
- "Merry Christmas Charlie Manson!" - Multiple duplicates seen with the kids in Nebraska.
- South Park: Bigger, Longer & Uncut
- "Hooked on Monkey Phonics"
- "World Wide Recorder Concert"
- "Cartman's Silly Hate Crime 2000"
- "Do the Handicapped Go to Hell?"
- "Fourth Grade"
- "Trapper Keeper"
- "The Wacky Molestation Adventure"
- "Red Hot Catholic Love"
- "Fat Butt and Pancake Head"
- "Casa Bonita"
- "Douche and Turd"
- "You Got F'd in the A" - Briefly seen eating at Raisins.
- "Quest for Ratings"
- "Stupid Spoiled Whore Video Playset" - Seen being chased by Bebe at her "Stupid Spoiled Whore" party.
- "The Death of Eric Cartman"
- "Mystery of the Urinal Deuce"- Seen in the hallway and in the gymnasium.
- "D-Yikes!" - Seen leaving the school.
- "The List"
- "Canada on Strike"
- "Breast Cancer Show Ever" - Seen watching the fight between Wendy and Cartman.
- "Elementary School Musical"
- "Miss Teacher Bangs a Boy"-Seen in the hallway.
- "Butters' Bottom Bitch"- Seen in the cafeteria.
- "T.M.I."- Seen in the cafeteria and the hallway.
- "City Sushi" - Seen in assembly.
- "1%"- Seen at the assembly.
- "Faith Hilling" - Seen in the memeing class with the other fourth Grade students.
- "Jewpacabra" - Seen at the Easter egg hunt.
- "Butterballs" - Seen in the background in the cafeteria.
- "Cartman Finds Love" - Seen in the background in the school's hallways.
- "Raising the Bar" - Seen during the "Here Comes Fatty Doo Doo" video.
- "Going Native" - Seen eating in the cafeteria.
- "A Scause For Applause" - Seen in the background in the school hallways.
- "Let Go, Let Gov" - Seen eating in the cafeteria.
- "Stunning and Brave" - Seen in the school hallways.
- "Sponsored Content"- Briefly seen in the hallway.
- "Skank Hunt" - Seen in the school cafeteria and his girlfriend breaks up with him.
- "Wieners Out" - Seen participating in Butters' Wieners Out protest.
- "Douche and a Danish" - Seen in the battle between the boys and the girls.
- "Oh, Jeez" - Seen at the school assembly.
- "Holiday Special" - Seen rioting with the students, and seen in the crowd.