The opener of the 24th annual "Treehouse of Horror" is from Guillermo del Toro and features monsters and classic characters from horror films throughout history. In "Oh The Places You'll D'oh," the first of three spine-tingling stories, Homer rides around Springfield wreaking havoc as "The Fat in The Hat" in a rhyming Dr. Seuss-ian tale. In "Dead and Shoulders," Bart is beheaded during a kite accident, his head is attached to Lisa's body and they must live together as one. The final terrifying tale, "Freaks no Geeks," features Mr. Burns' traveling circus, The Burnsum and Bailey Circus, which has stopped in Springfieldland in the 1930s. Trapeze artist Marge and Strong Man Homer are performers and things go awry when circus freak Moe starts to make advances towards Marge.

Marge encourages Homer to embrace his "You-Only-Live-Once" spirit by inviting an old pen pal to stay with him and cross items off of his "to-do" list from when he was a 10-year old. Meanwhile, Lisa institutes a new honor code at Springfield Elementary. Blackboard: 'My school schedule does not include a bye week'.