Say It Isn't So is a 2001 American black comedy film directed by J. B. Rogers, written by Peter Gaulke and Gerry Swallow, and starring Heather Graham and Chris Klein as two young lovers who come to believe that they are actually siblings.

Heather Joan Graham is an American actress. After appearing in television commercials, her first starring role in a feature film came with the teen comedy License to Drive (1988), followed by the critically acclaimed film Drugstore Cowboy (1989). She then played supporting roles on the television series Twin Peaks (1991), and in films such as Six Degrees of Separation (1993) and Swingers (1996). She gained critical praise for her role as "Rollergirl" in the film Boogie Nights (1997). This led to major roles in the comedy films Bowfinger and Austin Powers: The Spy Who Shagged Me.