Marge-bot

The Marge-bot was a robotized version of Marge. Homer had a brief fantasy about her.

History
Springfield Elementary School installed vending machines, and Bart quickly became hooked on the junk food they dispensed. At dinnertime at home, he refused to touch Marge's tuna steak, saying, "The vending machines at school feed me now." Marge, annoyed, said, "Oh, so I've been replaced by a machine?"

Homer, reassuring her, said, "Marge, no machine could ever replace you", but then thoughtfully said, "Or could it?" as he drifted into a fantasy.

In his fantasy, Homer came home, hung up his hat and said, "Oh Marge-bot, I'm ready for some lovin'!" The Marge-bot, carrying a machine gun, strode into the entryway. Then she raised her gun and opened fire, riddling Homer with bullets.

Abruptly kicked out of his fantasy, Homer lamented, "Why did I give her a gun?" Then, fully returning to reality, he said firmly, "But I repeat: No one is being replaced by a machine ... until all the kinks are worked out."

Behind the Laughter

 * The Marge-bot resembles the Terminator, in both appearance and behavior.
 * The Marge-bot could be considered the fulfillment of the "Marge becomes a robot" plotline, suggested in the closing song of "Gump Roast".