Mimsy is a mentally disabled boy, who is also Nathan's henchman in the episode "Crippled Summer" of South Park.
When Jimmy Valmer and Timmy return to Lake Tardicaca, a camp for handicapped children, Jimmy unknowingly finds himself to be targeted by his former-drug dealer and leader of the Red Camp Game team, Nathan, who has developed a great dislike for Jimmy due to the fact that Jimmy has led the Blue camp team to victory 3 years running. Aiding Nathan is Mimsy, a big, strong, but dimwitted lackey, who inadvertently causes all of Nathan's plans aimed at defeating the Blue team and killing Jimmy, to backfire.
Nathan's first plan is to put a Black Mamba snake into the Blue Team's canoe. However, his orders to Mimsy are "Put the snake in the canoe", making Mimsy assume that Nathan meant for him to put the snake in their team's canoe, rather than Jimmy's. Similar errors involve a map leading to an Indian reservation, who's Indians kill on sight during the Scavenger Hunt, a shark-mating whistle during the surfing competition (that results in Nathan being raped by a shark), and an exploding ukulele. He is based off Mugsy from Looney Tunes.