In the kitchen, Homer lights up a Jack-O-Lantern, but ends up lighting his hand on fire. He runs off and on the screen screaming while the title is shown. The couch gag depicts a grim reaper sitting on the couch, and the family suddenly falls and dies instantly in front of him. The grim reaper then relaxes and places his legs on the pile of Simpsons corpses.
The Thing and I
In a parody of The Hunchback of Notre Dame and Basket Case, Bart, Lisa, and Maggie begin to hear strange noises coming from the attic one night. The next morning, after they mention this to their parents, Marge reminds Homer to feed the "thing". The kids spy on Homer climbing to the attic feeding fish heads to something. They are still curious as to what this is, and Homer accidentally calls them four children when he said "I work my butt off to feed you four kids", until Marge covers it up. That night, while Homer and Marge are out, the kids sneak into the attic, where Bart discovers the unsold copies of Homer's autobiography. They find a shadow, see a figure with a maniacal laugh, and run out of the attic scared. Homer and Marge come home disappointed to find out that they entered the attic when they specifically said not to. When they climb up into the attic, the weird shadow escapes, with marks left on the front door. Marge calls Dr. Hibbert to inform him that Hugo is loose. Bart asks who Hugo is, and she then tells Bart that he has a twin brother. Dr. Hibbert suddenly appears, scaring Marge, and explains the story of Hugo. When Bart was born, he was a siamese twin (although he meant conjoined). The only problem was that the left twin was evil. So after they were separated, Homer and Marge planned to chain Hugo up in the attic and feed him fish heads. Bart believes this story when he discovers his scar. Everyone except him exits the house to find Hugo, leaving Bart behind, who knows that Hugo is in the house. He soon realizes that he is right, as Hugo confronts him. Hugo ties him up on a table in the attic planning to sew them back together in hopes of becoming sane again. Before the operation begins, Dr. Hibbert appears and shows Hugo a mirror to see his own face in, but Hugo becomes confused as it has no glass, and Dr. Hibbert punches Hugo in the face, knocking him out. He then notices that Hugo's scar is on the left side. Remembering that the twin on the left was evil, he reveals that Bart was the evil one and that he gave them the wrong twin. Bart responds by telling them not to look so surprised. The next scene shows a failed attempt to correct their wrong, Hugo rejoining the family while still somewhat demented from years of living in the attic, Bart who has taken Hugo's place in the attic asks for some turkey through the air vents in the dining room but Marge says for him to finish his fish heads and closes the grate.
The Genesis Tub
In a parody of the Twilight Zone episode, The Little People, Lisa places a tooth in cola for a school science project. After being shocked by static electricity from Bart, Lisa touches the tooth, and the spark causes life to evolve in the petrify dish where the cola and tooth are. In less than a few days, the tiny people have evolved to a futuristic cityscape. However, Bart playfully destroys some of their tiny buildings, causing them to launch a counterattack, sending a small fleet of aerial vehicles to attack him. Bart wants to destroy them for attacking him, but Lisa intervenes. He leaves, threatening that he will get revenge on them. Shortly after this, a strange beam from the petri dish hits Lisa, shrinking her down and into the tooth city, where she finds she is hailed as a god and Bart as the devil. The citizenry ask her for many answers, to which she promises she can help if she were big again. However, the people have not figured the technology to enlarge things. Matters turn worse when Bart claims the petri dish and the civilization as his own, winning the school science fair. Realizing she is trapped with the tooth city's inhabitants forever, Lisa settles in to become their ruler, beginning by ordering them to bring her some nice shoes to replace her now gone slippers, and some socks, too.
In a parody of the 1941 drama film Citizen Kane, while Homer is out fishing one night, the two aliens Kang and Kodos capture Homer and ask who his leader is. Homer tells them that the election is next week so the new president may be either Bob Dole or current president Bill Clinton. Upon hearing about this, the two aliens decide to kidnap both candidates and take their forms. Before dumping Homer off of their ship, Kang sprays him with rum so that no one believes him. On the day of the election, Homer stumbles upon Kang and Kodos' ship and goes inside to set the real Bill Clinton and Bob Dole free, but he accidentally pilots the ship into space. Bill Clinton and Bob Dole agree on leading the country together and ask Homer to let them out. However, Homer accidentally ejects them from the ship and they die from the lack of oxygen while floating into the dark void of space. Having failed to rescue the candidates, Homer then crashes the ship into the White House, climbs down, and exposes Kang and Kodos to be aliens, much to everyone's surprise. Despite not being the real competitors, the people have to vote for one of them anyway. One of the citizens suggest a third-party vote, and Kang replies, "Go ahead, throw your vote away." Eventually, Kang wins the election, and as the president, he and the Rigellians enslave the whole entire country to build a giant laser cannon to fire at a planet the humans have never even heard of before. Marge comments why they have to do so, and Homer replies, "Don't blame me, I voted for Kodos", but is whipped by a Rigellian.
This episode (more specifically, The Genesis Tub) was referenced in the South Park episode, "Simpsons Did It"
This is the second Treehouse segment to feature Kang and Kodos in a main role since Hungry are the Damned in Treehouse of Horror.