Dr. Tess Coleman (Curtis) and her fifteen-year-old daughter, Anna (Lohan), are not getting along. They don't see eye-to-eye on clothes, hair, music, and certainly not in each other's taste in men. One Thursday evening, their disagreements reach a fever pitch - Anna is incensed that her mother doesn't support her musical aspirations and Tess, a widow about to remarry, can't see why Anna won't give her fiance (Harmon) a break. Everything soon changes when two identical Fortune Cookies cause a little mystic mayhem. On the next morning, their Friday gets freaky when Tess and Anna find themselves inside the other's body. As they walk a mile in each other's shoes, they gain a little newfound respect for the other's point of view. But with Tess's wedding coming on Saturday, the two have to find a way to switch back (and fast).