Prelude to a Kiss
An old guy (Sydney Walker), unhappy with his life, sneaks into Meg Ryan's wedding, and when he kisses her, they exchange bodies. Alec Baldwin starts getting suspicious about the change in his new wife's behavior, and one day the old guy (with Meg Ryan's spirit) appears at his door and convinces him (Alec) of who he (she) really is. They plot to get the spirits back into the right bodies and are successful (after another kiss).
Thanks, Lynn E!