Revenge Gone Awry

That was the theme of this Simpsons episode. A funny episode, at that.
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The Simpsons Season 18 Episode 11 Quotes

(to Milhouse) Ha ha, you forgot me because I had the mumps!

Nelson

Thank you, masked vigilante. Your over-zealous homicide has saved me 80 cents. Now if you're not going to buy anything, please move along.

Apu