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 mostly 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 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 eventually got his first full speaking appearance in South Park: The Fractured But Whole as one of the boys inside Raisins. His voice sounds like a hybrid between Kyle and Clyde's voices. 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 step up 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.
In "Skank Hunt", Isla breaks up with Brimmy due to the conflict between the boys and the girls.
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 clothing. Underneath his hat, as shown in "Super Fun Time", he has shoulder-length, wavy blond hair.
- The South Park crew refers to this character as "Kid A", since he was one of the first background characters created when production of the series switched from paper to computers.
- Brimmy is spotted in the third grade classroom in the episode "Gnomes", sitting next to Pip Pirrip and Token Black.
- Brimmy bears a resemblance to the Girl with Blonde Hair; the two both have very similar clothing and have identical hair.
- The Unaired Pilot
- "Cartman Gets an Anal Probe"
- "Mr. Hankey, the Christmas Poo"
- "Tom's Rhinoplasty"
- "Conjoined Fetus Lady"
- "Summer Sucks"
- "Merry Christmas Charlie Manson!" - Multiple duplicates are 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"
- "Toilet Paper" - Seen in the hallway.
- "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 movement.
- "Douche and a Danish" - Seen in the battle between the boys and the girls.
- "Oh, Jeez" - Seen at the school assembly.
- "Holiday Special" - Seen in the hallway rioting due to a cancellation of Columbus Day, and seen in the crowd.
- "The Problem with a Poo" - Seen in the school assembly.
- "Shots!!" - Seen on the Main Street when Randy is celebrating.
- "Let Them Eat Goo" - Seen in the cafeteria and at the assembly.
- "Tegridy Farms Halloween Special" - Seen at the school assembly.
- "Board Girls" - Seen at the school assembly.
- "Basic Cable" - Seen in the school bus.