Homer's brain quits

This came during a stretch when the writers kept making Homer dumber and dumber, until they drew the line at his ever forgetting his own name.

The policeman asks Homer to explain himself, and Homer mutters to himself: say something good, say something good, say something good. Then Homer announces that he's watching pornography.

The show cuts to inside his head, where his brain has been repeating the same instruction. Homer has said the exact wrong thing. Cut back to the brain, which announces that's it, it's out. Footsteps, and then a door slam.