Billy and Mandy tell Grim it is "Opposite Day" and that, when they say something, they really mean the opposite. Due to his difficulty understanding the concept of Opposite Day, Grim has to do Mandy's chores. Finally, Grim thinks he understands when Billy and Mandy say they "want" pie, meaning they "do not want" pie. However, Mandy then says that when she said it was Opposite Day, it really was not. Major Doctor Ghastly makes her latest world-domination device, but General Skarr, Con Carne's Chief of Staff, uses the giant robot dog (modeled after Con Carne's tiny little chihuahua, Enrique Jr.) to attempt to kill Boskov and Con Carne instead of trying to take over the world with it. Grim is bored of being left alone while Billy and Mandy are not with him. Grim decides to fulfill his dream by working as a swimsuit model, but, as he is a corpse, he is not hired. Subsequently, Billy and Mandy give him a makeover to look more human.