The traditional meaning of that is, a person having stupid reasons all the way or a person having disgusting attitude (or set of teeth.)
Hirokazu: Shut up! You're such a bungal!
Denmark: No, I'm not!
Hirokazu: Yes, you are! Good thing I'm not.
Extra Kid#1: Smile!
Hirokazo Ono and Denmark Martinez: F*ck Up!