Take a movie, change a element, decision or whatever to 'ruin' the movie.
Example:
INTERIOR: IMPERIAL STARDESTROYER.
On the main viewscreen, the lifepod carrying the two terrified
robots speeds away from the stricken Rebel spacecraft.
CHIEF PILOT: There goes another one.
CAPTAIN: Hold your fire. There are no life forms. It must have been
short-circuited. On second thought. Shoot it down. Just it case.
EXTERIOR: LIFEPOD CARRYING R2-D2 and C3PO explodes.