[Aang puts on a sinister smile, remembering how poetic she got about spooky stuff at Nami's party.]

They call it... Koh. [Dramatic pause] The face stealer. His body looks like a big ol' bug. And his face? He can change it whenever he wants, to any of the faces he's stolen. When you meet him... you can't let him see you making any expression at all. Because that's when he can take your face, for his collection...