Theo sends away for a practical joke kit. He succeeds in playing pranks on most of the family, but Cliff is not fooled. He boasts that no one could ever pull a joke on him. Sondra and Elvin arrive unexpectedly while Cliff is at the hospital. The family is thrilled when they announce their engagement. They decide to use the fact that Cliff is the only one who hasn't heard the couple's big news to set up a prank. Elvin visits Cliff's office and tells him that he plans to propose to Sondra over dinner. However, he claims that he fears that Clair hates him because of his sexist comments of the past. He asks Cliff to talk to her on his behalf. Clair feigns outrage when Cliff mentions the possibility of Elvin proposing to her daughter, even bellowing that the proposal would be the last words he would ever utter. Elvin pretends to cry and says that Cliff has let him down. Cliff takes Elvin to the kitchen and has him share his more modern views of women, but Clair scoffs that Elvin is putting on an act. Cliff is extremely bewildered. However, he overhears the rest of the family laughing about the prank and discussing plans for that evening. Cliff gets back at them during dinner by pretending to yell at Elvin and throw him out of the house. He taunts them about failing to keep him from learning about the joke. Elvin formally proposes to Sondra, and everyone welcomes him to the family. When Cliff shakes his hand, Elvin zaps him with a joy buzzer.