The Rotten Cupcake is a minor antagonist in The Amazing World of Gumball episode, "The Lesson." He is one of the bad Elmore Junior High kids who got a detention from Principal Brown. He did not like the prescence of Gumball and Darwin in the school cafeteria. He speaks when Gumball and Darwin are in detention. He is supposedly killed by the Pink Bear at the climax of the episode when all the bad kids are fighting each other as purple filling akin to blood is seen splattered on the door window, except for the Bomb Guy who was attempting to escape.
He is very mean and cruel and is also able to read thoughts, as shown when Gumball and Darwin are talking to themselves with their minds.