"Treehouse of Horror XVI"' is a Halloween-themed episode from the seventeenth season of the animated comedy series The Simpsons. It was first broadcast in the United States on the Fox Network on November 6, 2005, in the United Kingdom on Sky 1 on December 18, 2005 and in Australia on Channel 10 on February 28, 2006.
In common with all the previous "Treehouse of Horror" episodes of The Simpsons, the program is made up of three self-contained stories; "B.I.: Bartificial Intelligence", "Survival of the Fattest" and "I've Grown a Costume on Your Face". In the first story, which parodies the 2001 science-fiction movie A.I.: Artificial Intelligence, Bart Simpson risks being replaced by a robot. The second story, which spoofs Richard Connell's 1924 short story "The Most Dangerous Game", sees Homer Simpson and the other men of Springfield get invited to a hunting party, in which they are the hunted, not the hunters. In the final story, a witch casts a spell on the people of Springfield, making them change into the things which their Halloween costumes represent.
The aliens Kang and Kodos are unhappy because, due to the Fox Network's coverage of the baseball World Series, the Halloween episode of The Simpsons has been delayed until November. They fear that it will be further delayed if the World Series does not finish soon and decide to speed up the baseball game. The players move faster and faster, eventually creating a vortex. The vortex sucks in the surrounding area, the oceans, the entire Earth, the solar system, the universe and God.
Kodos criticizes Kang for having made the universe disappear. Kang says that there is nothing to worry about because he will leave a note. A yellow Post-it note marked "Treehouse of Horror XVI" is placed in the center of the black screen.
"B.I.: Bartificial Intelligence"
After attempting to jump from a roof into a swimming pool, Bart Simpson is left in a coma. Missing their son and brother, Bart's family buy an android in the form of a boy. The android, named David, soon proves to be an ideal brother and son. When Bart recovers, he is forced to compete with David for the affections of his mother Marge and his father Homer. Marge is not happy about the rivalry between Bart and David. Homer says that he will sort it out, which he does by abandoning Bart in the woods.
Bart soon comes into contact with some old abandoned robots. He takes parts from the robots' bodies and adds them to his own, turning himself into a powerful cyborg. Bart returns to his family home and attacks Homer and David, slicing them both in two. Having lost his legs, Homer takes those of the robot David.
Homer Simpson wakes up, the entire story has just been a dream. Homer is relieved to find out that he is not half robot but is reminded that he is possessed by the Devil.
"Survival of the Fattest"
Homer Simpson and many of the other men of Springfield are invited by Mr. Burns to attend a hunting party at his mansion. The men are unaware that they are to be the quarry. Burns' human hunt is shown on live TV.
The men gradually fall victim to Burns, die accidentally or are eaten by the other survivors, leaving Homer Simpson as the last one left alive. Just as he is about to be shot by Burns and his assistant Smithers, Homer is saved by his wife Marge, who knocks out both Smithers and Burns with a frying pan. Marge then strikes Homer as well, for having been absent for eighteen hours without calling home.
"I've Grown a Costume on Your Face"
On Halloween night, the people of Springfield gather in the town square in their costumes. Homer Simpson is dressed as a headless man, his wife Marge is dressed as a skeleton, his son Bart is dressed as a werewolf, his daughter Lisa is dressed as Albert Einstein and his baby daughter Maggie is dressed as a witch.
A competition is held in which a prize is awarded to the person in the best costume. The prize is won by a woman dressed as a witch, whose costume is so good that nobody recognizes who she really is. When she is asked to reveal her ientity, she is forced to admit that she is a real witch. She is immediately stripped of her prize, on the grounds that she is not wearing a costume. The furious witch takes her revenge on the people of Springfield, casting a spell which makes each person become the thing his or her costume represents. Homer Simpson's head falls off, Marge becomes a skeleton from the neck down, Bart becomes a werewolf, Maggie becomes a witch and Lisa becomes a genius with white hair, a bushy mustache and a German accent.
Lisa tries to use her newly enhanced intelligence to think of a way to break the spell. When she remembers that her baby sister has become a real witch, she declares that Maggie should be able to undo the spell. The people of Springfield are told to gather at the Simpsons' house to be returned to normal, although some protest that they do not want to be changed back and are happier than before they were transformed. The baby witch casts a spell but it does not return everybody to normal. Instead, Maggie changes all the people of Springfield into giant living pacifiers with human heads, before flying away on her broomstick.