When I decide to take in a movie at the theater, it's a sort of Golden Rule of mine to get there at least twenty minutes before showtime. This is mostly in order to secure a good seat, but there's also the pre-show reel to watch. This usually consists of behind-the-scenes style promos for upcoming movies/shows. Afterwards, the reel shows everyone who didn't watch it what they missed.
College Humor devised a version of that summary for the theater crowd, itself.