Professor Sherman Klump is getting married. And the Klump family could not be more delighted for him. But Buddy Love, his Mr. Hyde alter-ego from the first film, is back and trying to make it on his own. Buddy keeps resurfacing in untimely outbursts, and threatening the portly professor's marriage plans to colleague Denise Gaines. Utilizing Denise's cutting-edge DNA research, Sherman decides to rid himself of his monstrous nemesis -and his disruptive outbursts-once and for all by extracting...

Martin Blank is a freelance hitman who starts to develop a conscience, which causes him to muff a couple of routine assignments. On the advice of his secretary and his psychiatrist, he attends his 10th year High School reunion in Grosse Pointe, Michigan (a Detroit suburb where he's also contracted to kill someone). Hot on his tail are a couple of over-enthusiastic federal agents, another assassin who wants to kill him, and Grocer, an assassin who wants him to join an "Assassin's Union."