Those Daring Young Men in Their Jaunty Jalopies.

This is the only movie I have ever walked out.
My roommate and I were on a double date. We went to this movie; it was supposed to be a cross between
Those Magnificent Men in Their Flying Machines and
The Great Race, both of which are very good. This one isn't.
Part way through, my roommate excused himself to go to the men's room. Shortly after, his date excused herself to go to the snack bar.
My date and I sat and watched and waited for them to return. After 15-20 minutes, we decided that the movie was awful and we weren't waiting for them to come back, we were leaving.
As we started back up the aisle, there they were, sitting a few rows back, grinning broadly. They, too, had decided the movie stunk and were waiting to see how much more we'd take before leaving.