A prequel to a sequel, or a movie in a series in which none of the original characters could appear ie: Alien vs. Predator. It occurs before the original Alien movies, yet after the original Predator movies, therefore characters from either series could not have a role.
Joe:Why doesn't Danny Glover just pop up and fuck up the Predators, and Sigourney Weaver could handle the Aliens?
Scott: Because he's old as fuck by now, and she's not even born.
Joe: Wait what? Isn't this a sequel?
Scott: Nah man, it's a fuckin' Deeker.