Oh, TIS, that's too bad! It reminds me of when my brother saw Jaws for the first time. SPOILER (as if there may be anyone left who hasn't seen it)

It's the end, and the Orca is sinking, and Brody feeds the shark the scuba tank and grabs his rifle. The shark is coming back at him, and all of a sudden, it flashed to the scene where Quint is talking about being on the Indianapolis. At first, my brother thought it might be a flashback, but the scene continued to play. All of a sudden, this screaming and cursing and crashing was heard from the projectionist's booth. Obviously, somebody had cued up the wrong reel. My brother said it sort of ruined the movie, although they finally did get it right, but he laughed his ass off for weeks afterwards!!