I should probably warn you that this is full of spoilers for Twilight: Breaking Dawn. Everything that happens in the video, I shit you not, is canonical. As the movie’s title says, This Actually Happens In Twilight: Breaking Dawn.
Hat tip to Rebecca Watson at Skepchick.org. No, wait, not hat tip. “I hate you.” The less I know about Stephanie Meyer’s masturbatory Mormon vampire fantasies, the better.