Clips from the "French Mistake" episode of the TV show "Supernatural". The two brothers Sam and Dean hunt demons, vampires, ghosts, etc and in general deal with all kinds of supernatural phenomena. In this episode somebody needs to protect them from imminent attack and so transfers them to an alternate universe, which turns out to be the set of their own TV show "Supernatural". When they finally figure out what's going on they have to play along for awhile until they can think of a way to get back to their supernatural world. It's hilarious watching them trying to play the actors who play themselves.

It's a very clever episode and they get in all kinds of digs at themselves and the production staff. The "French Mistake" refers to the dance routine scene in "Blazing Saddles" where the characters also step out of the movie and are seen in the actual production set of the movie.