Sonny Koufax (Adam Sandler) is a thirty-two-year-old loser who refuses to take responsibility for his life and spends his days watching television in his pyjamas. The day after his girlfriend Vanessa (Kristy Swanson) dumps him, five-year-old Julian (Cole and Dylan Sprouse) arrives at his house, claiming to be the son of his recently departed flatmate. Sonny then mistakenly decides that adopting Julian will impress Vanessa, only to discover that there is more to parenting than meets the eye.