Jack Sadelstein (Adam Sandler) is a successful advertising executive in Los Angeles with a beautiful wife (Katie Holmes) and kids, who dreads one event each year: The holiday visit of his identical twin sister Jill (also Adam Sandler). Jill's 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 she'll ever leave!