bimbo
n. a clown-like person.What a silly bimbo!If that bimbo doesn't keep quiet, I'll bop him.
bubblehead
n. a fool; a giddy person.You silly bubblehead. Watch where you are going!If you can't say anything without coming off like a bubblehead, keep your mouth shut.
ditz and ditzo
n. a giddy, absentminded person.You silly ditz!I'm getting to be such a ditz!Who is the ditzo on the phone? Another wrong number?
flake
n. a person who acts silly or giddy.Sally is such a flake!Who's the flake in the plaid pants?
fruitcake and fruit loop
n. a foolish oaf. (Someone who is as nutty as a fruitcake.)What a fruitcake! Doesn't even know where his head is at.Carl acts like such a loony fruit loop.
gonzo
n. a silly or foolish person.Some gonzo is on the phone asking for the president of the universe.Tell the gonzo I'm out.
space cadet
n. a person who is always silly or giddy.Mom, you are such a space cadet.Here comes a space cadet who looks like he has more money than he needs.
space out
n. a giddy person. (Usually space-out.)Terry is becoming such a space-out!What a space out you are!