FOOL NOTION
Synonyms and related words:
absurd idea, boutade, brainstorm, capriccio, caprice, conceit, crank, craze, crazy idea, crotchet, fad, fancy, fantastic notion, fantasy, flimflam, freak, freakish inspiration, harebrained idea, humor, kink, maggot, megrim, notion, passing fancy, quirk, toy, vagary, whim, whim-wham, whimsy