The plot involves Luigi drinking some prune juice. His stomach growls, and Luigi notices he has to go potty. He goes to his bathroom and makes his doody, then flushes the toilet. However, since his plumber has done a crappy job, the toilet shoots dung everywhere like a geyser.
King and Queen Boo, meanwhile, view this as the perfect opportunity to destroy Luigi. They bring the poopy to life, and it begins attacking Luigi. Fortunately, Prof. E. Gadd shows up and gives Luigi a vacuum cleaner, which somehow kills the dung. It also had this charger called the FecalMatter 9000. While you are charging you have to use the Pooper Scooper.