19 possible answers to
Answers with 3 characters: MAD NUT Answers with 4 characters: KOOK LOCO LOON NUTS ZANY Answers with 5 characters: CRAZY LOONY Answers with 6 characters: INSANE LOONEY MANIAC NUTJOB Answers with 7 characters: LUNATIC BANANAS NUTCASE Answers with 8 characters: BUGHOUSE UNHINGED Answers with 9 characters: SCREWBALL