Synonyms for Prank (same or very similar meaning)
WordNet sense 1 (acting like a clown or buffoon):
buffoonery, frivolity, japery, clowning, harlequinadeWordNet sense 2 (a ludicrous or grotesque act done for fun and amusement):
antic, caper, joke, put-on, trickFrom the ODE community, based on WordNetadd/edit