Related Clues:

• Bart Simpson hears it a lot
• Homer Simpson utterance
• Noted cartoon catchphrase
• "Silly me!"
• Cato's 102
• Response to dropping donuts and so forth
• 2001 OED addition that cites "The Simpsons"
• 102, to Caesar
• "Am I an idiot!"
• Second century date
• Word spoken with a head slap
• Homer holler
• Cry accompanying a head slap
• MXX ÷ X
• Homer Simpson's cry