Dickie Roberts (DAVID SPADE) is a 35-year-old parking valet who's fallen on hard times, as he's never been able to match the success of being a former child star on the 1970s TV sitcom, "The Glimmer Gang." When not hanging out with fellow former child stars and performers, or having his girlfriend, Cyndi (ALYSSA MILANO), dump him, Dickie hopes that his agent, Sidney Wernick (JON LOVITZ), can get him an important part that will begin his comeback.
He gets that chance when he hears that director Rob Reiner (ROB REINER) is casting for his next picture. Reiner thinks that Dickie is physically perfect for the part, but worries that since Dickie never had a normal childhood, he might not be able to handle the emotional aspect of the role.
With a few months before Reiner makes his final decision, Dickie decides to hire a family to teach him what it's like to grow up in a normal household. Accordingly, he shows up at the steps of the Finney house where car salesman dad George (CRAIG BIERKO) has agreed to the arrangement without first consulting his wife, Grace (MARY MCCORMACK), or their young kids, Sam (SCOTT TERRA) and Sally (JENNA BOYD).
None of the latter are particularly thrilled about the prospect of a stranger moving in with them for a month. Despite that and various setbacks along the way, however, they eventually come to like and help him, just as he does for them, all while hoping to learn enough to land the lucrative part.