High Quality Content by WIKIPEDIA articles! "Treehouse of Horror XVIII" is the fifth episode of The Simpsons` nineteenth season and was first broadcast on November 4, 2007. 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. and Mrs. Simpson," and Ned Flanders is given God-like powers during his demonstration on the wages of sin in "Heck House." It was written by Marc Wilmore and directed by Chuck Sheetz.