Phrase referring to when someone quotes, cites, or uses something that was previously done on The Simpsons. Thus, they are making a Simpsons reference.

This wonderful phrase can be used in virtually any setting, time or place.
Guy 1- "Ow! I dropped a hammer on my foot, dammit that hurts!"
Guy 2- "Haw-haw" (ala Nelson)
Guy 3- "Simpson's reference!"

Corporate Accountant- "Mr. CEO, our profits will increase by 42% over the next year due to this new project."
CEO (tapping is fingers together)- "Excellent"
Accountant- "Simpsons reference!"
by ACG2x December 2, 2004