"Treehouse of Horror XVIII" is the fifth episode of the nineteenth season of the American animated television series The Simpsons.

In the eighteenth annual Treehouse of Horror episode, Bart harbors Kodos the alien in "E.T., Go Home," Homer and Marge are husband and wife assassins who try to take each other out in "Mr. & Mrs. Simpson," and Ned Flanders is given God-like powers during his demonstration on the wages of sin in "Heck House."

When NASA agents arrive at the Simpsons home, Homer distracts them by dressing as Abraham Lincoln while Bart sneaks Kodos out.

A brief war is waged, and Earth ultimately overpowers the aliens (the massive heads of Kodos' species make them easy targets for attack helicopters).

After Chief Wiggum interrupts with a complaint from an "anonymous neighborino", Marge shoots him with a crossbow, killing him (even though he states he would have taken a bribe).

For this, they soon begin making love over Wiggum's body and, back to where the episode started, they both realized that they did not need any marriage counseling, but to kill people together.

Soon, however, their pranks shift into vandalism (and even thievery when they tie up Lenny and steal his TV), and their victims gather at the Simpson house to complain.

However, the pranksters scoff at his attempt, causing Ned to angrily turn to the heavens and ask for the power to "psychologically torture" the kids into loving God.

Lightning flashes and Ned is transformed into the Devil (reprising his role from "Treehouse of Horror IV" though lacking goat legs), and then sends the kids to Hell.

The crystal ball shows: A wider view of Hell is then shown, with various citizens of Springfield being punished for their sins on Earth, in a reference to the Inferno section of Dante's Divine Comedy.

On July 27, 2007, creator Matt Groening and the producers attended a panel which encompassed the topics of both The Simpsons Movie, and the nineteenth season.

The panel revealed that Peter Griffin from Family Guy is one of the miniature characters featured in the opening sequence, although he appears as a cameo from the scene.

Lisa says "I can't believe that an alien who looked so evil turned out to be bad", a reference to Arthur C. Clarke's Childhood's End.

[3] Hell, as depicted in "Heck House" is inspired by The Garden of Earthly Delights painted by Dutch Renaissance painter Hieronymus Bosch.

[5] Combined with a new episode of Family Guy, it tied for first in the 8:00 PM hour with the NFL Pregame show on NBC.