A group of students once put me up to pranking their friend over a lunch period.
They'd all been egging houses one night and actually got away with it (an act I DON'T condone), but a few thought it'd be funny to have me call one of them, posing as a police officer who'd been informed of whole ordeal. Half an hour later, the student I had called and issued a COURT ORDER on, was sittingright next to me for an entire class, pale as a ghost.
As an actor, I think this was my absolute proudest moment.