 FAKE: When Biff starts in on Marty with "You think that stupid  disguise is gonna get past me?" he challenges Marty to a fight and  Marty says, "No, Thanks," and turns to exit the shot. The edge of  the window in the background is the split. When Marty turns, the  brim of his hat just barely crosses the line, causing it to  disappear for a few frames.