(n.) A hobby ; freak; whim.

best seller big hit boutade brainstorm brilliant success capriccio caprice chic conceit crank craze crazy idea crotchet cry faddiness faddishness faddism faddist fancy fantastic notion fantasy flimflam fool notion freak freakish inspiration furore gas gasser great success harebrained idea hit humor killing kink maggot megrim meteoric success mode momentary success notion novelty passing fancy quirk rage resounding triumph riot roaring success sensation smash smash hit style toy triumph vagary vogue whim whim-wham whimsy wow wrinkle