Nick Twisp (MICHAEL CERA) is a young high school student who lives with his mom, Estelle (JEAN SMART), and her good for nothing boyfriend, Jerry (ZACH GALIFIANAKIS), while his unemployed dad, George (STEVE BUSCEMI), lives elsewhere with his much younger trophy girlfriend, Lacey (ARI GRAYNOR). To complete Nick's odd world, neighbor Mr. Ferguson (FRED WILLARD) harbors illegal immigrants in his basement.
Except for his best friend, Lefty (ERIK KNUDSEN), Nick thinks he's the unluckiest guy in the world when it comes to girls and losing his virginity, but things unexpectedly look up when his mom and Jerry take him on an impromptu vacation. Arriving in a trailer park, Nick meets Sheeni Saunders (PORTIA DOUBLEDAY), a pretty girl whose worldly ways -- as is the case with her druggie brother, Paul (JUSTIN LONG) -- makes it seem as if she comes from different parents than her ultra-religious and conservative mom (MARY KAY PLACE) and dad (M. EMMET WALSH).
Despite her seemingly liking Nick, Sheeni informs him that she has a boyfriend, Trent (JONATHAN BRADFORD WRIGHT), something later confirmed by her classmate, Vijay (ADHIR KALYAN), who soon becomes Nick's close friend. Accordingly, Nick doesn't think he has much of a chance with Sheeni, but she seems to be leading him on, and thus when she suggests he should be bad, he concocts an alternate personality.
While Nick is the only one who can see French playboy Francois Dillinger (MICHAEL CERA), the aggressive sociopath leads Nick down a path of bad behavior, eventually drawing the ire of local cop Lance Wescott (RAY LIOTTA) who starts seeing Estelle once Jerry's out of the picture. From that point on, and as things go from bad to worse for Nick, he continues his hopeful quest of losing his virginity to Sheeni.