Jack Sadelstein (Adam Sandler), a successful advertising executive in Los Angeles with a beautiful wife (Katie Holmes) and kids, dreads one event each year: The holiday visit of his identical twin sister Jill (also Adam Sandler). Jills neediness and passive-aggressiveness are maddening to Jack, turning his normally tranquil life upside down. Things spin even more out of control for Jack when Jill decides to extend her visit-and he doesn't think that shell ever leave!