April Fool's Day (1986)
Don't let the joke be on you!
When wealthy Muffy St. John invites her college friends up to her parents' secluded island home for spring break, they all arrive expecting a weekend of sun and sex. Things are fine at first, but when one of the guest goes missing, the weekend takes a turn for the worse and only gets more horrible from there. But as bodies begin to pop up left and right, the guests have to remind themselves that Muffy always was a big practical joker--the trouble lies in trying to determine what is real and what isn't!