Silly Ol' Goomp
From the Super Mario Wiki
Captain Goomba, Captain Shy Guy, and Captain Boo encounter Private Goomp, who begins to battle the Goomba Squad after again accusing them of infringing on his personal goals. The captains and their squad are forced to battle Goombas, Pestnuts, Gritty Goombas, Paragoombas, and Private Goomp himself. After Private Goomp is defeated, Captain Goomba forcefully recruits him, thus "ending" the conflict.