Synonyms for Wacky:

adj.

absurd (adjective)
idiotic, screwy.
acting crazy (adjective)
foolish, silly, insane, zany, nutty, daft, absurd, balmy, preposterous, lunatic, loony, demented, nuts, screwy, mad.
amusing (adjective)
comical.
deranged (adjective)
nutty.
foolish (adjective)
imbecilic, cockamamy, tomfool, loopy.
haywire (adjective)
haywire.
insane (adjective)
crackers, balmy, bananas, fruity.

n.

amusing, hysterical, priceless, imbecilic, dippy, nonsensical, knowledge, ability, unearthly, jerky, mad, softheaded, wry, lunatic, absurd, humorous, tomfool, hilarious, dopey, comic, harebrained, comical, playful, moronic, preposterous, cockeyed, idiotic. wacky (noun)
cracked, buggy, around the bend, daft, fool, dotty, cockamamy, cockamamie, kooky, round the bend, nuts, batty, bats, crackers, loopy, loony, haywire, insane, barmy, unreasonable, kookie, goofy, whacky, nutty, loco, balmy, silly, bonkers, foolish, zany, sappy, fruity.

Other synonyms:

mentally ill, jerky, dippy, softheaded, brainsick, bananas, Daffy. maniacal, preposterous, imbecilic, absurd, moronic, lunatic, cockeyed, unbalanced, distraught, non compos mentis, nonsensical, screwy, demented, harebrained. disordered, unsound, moonstruck, idiotic, touched, dopey. mad, unearthly. off. Other relevant words:
demented, bananas, amusing, dippy, distraught, brainsick, comic, imbecilic, absurd, mad, idiotic, lunatic, mentally ill, cuckoo, non compos mentis, preposterous, unsound, screwy, harebrained, hilarious, touched, off, maniacal, Daffy, batty, softheaded, playful, cockeyed, dopey, comical, moonstruck, maniac, unbalanced, disordered, moronic, jerky, tomfool, nonsensical, unearthly.