Silly, crazy

He's loony enough to show up in a Mel Brooks movie

È talmente picchiato che non stonerebbe in un film di Mel Brooks

Heather is a beauty, but she's a loony too

Heather è una ragazza carina, ma un po' picchiatella

Loony is an abbreviation of "lunatic" from Latin LUNA, which means moon, as it was long believed that madness was related to the phases of the moon