Kwyjibo on the loose!

Bart: Here we go. Kwyjibo. [places his tiles] K-W-Y-J-I-B-O.
Twenty-two points, plus triple-word-score, plus fifty points
for using all my letters. Game's over. I'm outta here. [gets up]
Homer: [grabs Bart with his left hand, holding a banana in his right]
Wait a minute, you little cheater!
You're not going anywhere until you tell me what a kwyjibo is.
Bart: Kwyjibo. Uh... a big, dumb, balding North American ape. With no chin.
Marge: And a short temper.
Homer: I'll show you a big, dumb, balding ape! [leaps for Bart]
Bart: [making his escape] Uh oh. Kwyjibo on the loose!
-- Playing Scrabble (tm), ``Bart the Genius''