Peter is smitten by Jan's pretty classmate Kerry, whom Jan brings home from school one afternoon. Tongue-tied and shy, Peter has no idea how to break the ice with Kerry, so he enlists Greg's help (since Greg is supposedly a master with flirting and pick-up lines). Kerry, however, mistakenly concludes that Greg is the one interested in her, which causes friction between Greg and Peter. So to save the brotherly relationship between him and Peter, Greg enlists Marcia's help in a play act to convince Kerry that he is an aggressive, womanizing playboy so she'll lose interest in him. Peter arrives home and, unaware of the plan, tells Kerry that "Debbie" (Marcia) is their sister, and it was only an act. In the end, Peter's honesty wins Kerry's love.