Homer wins an eating contest against the mythical Cthulhu, Springfield is overrun by plant body-snatchers, Lisa finally snaps and Mr. Burns opens a retirement home with some Jurassic upgrades.
Segments
Intrusion of the Pod-Y Snatchers
Springfield is overrun by plant body-snatchers.
Multiplisaty
Lisa finally snaps.
Geriatric Park
Mr. Burns opens a retirement home with some Jurassic upgrades. There, they inject all of the senior citizens with dinosaur DNA.
Full Story
Opening Sequence
The episode starts in Fogburyport, birthplace of Green Clam Chowder. The Simpsons arrive there because a book stated it's a place to visit before they die. However, it was revealed to be a trap and that they will devoured by Cthulhu. However, Homer states that he was promised an oyster eating contest against Cthulhu, and he wins. As a reward, the family decides to eat Cthulhu.
Intrusion of the Pod-Y Snatchers
The segment starts off with an underwater base of Mapple where the late Steve Mobbs (on screen) tells the new Myphone and the new unfunny version of him to a hyper audience. When everyone is on their phone the unfunny Steve is revealed to be a plant alien on a mission. Now on the plant planet they shoot spores to Earth (going right next to the Futurama ship with a cloth saying "BRING BACK FUTURAMA" and then getting blown up). In Springfield, everybody transforms into plant versions. Comic Book states this is a homage to the movie Invasion of the Body Snatchers while the movie itself was a ripoff of The Thing When a plant version of Comic book guy says "pad" Milhouse and Bart get scared and run away. The Plant people see the citizens with pods (Mapple products) and ask where they found those. Bart says they found it under the living Christmas tree.
Multiplisty
After a sleepover at the the Van Houten Residence, Milhouse, Nelson, and Bart awake to find themselves inside a cell, suddenly freed by Penelope, the one that trapped them in it. Penelope, which is actually a multi-personalitied Lisa -- similar to James McAvoy's lead character in the M. Night Shyamalan film, Split (2016) -- acting strange, closes them in again after they don't ask for an encore on her performance.
Lisa attacks and kills Milhouse and Nelson, before Bart asks her what happened to her, to which Lisa tells the story: Bart grabbed Lisa's spelling test, changing her answers, mocking Miss Hoover and granting her a F. Lisa has a last change and gives Bart a last chance to save himself and he redeems himself, saving himself from being killed by trash, while Milhouse was transformed into a "paper boy".
Geriatric Park
Mr. Burns opens up a Jurassic-themed retirement home, a park filled with elders rejuvenated mixing their DNA with dinosaurs'. He brings Springfielders to the park, showing them the new "retirement home". At first they're all human, healthy and feeling young again, with incredible strength too, but once Homer raises the temperature after Grandpa complains about the temperature being too cold, they transform into dinosaur creatures.
Visitors and Mr. Burns are killed by the elders, while the Simpson family are threatened by Grandpa and Jacqueline Bouvier, but Lisa courageously confronts Grandpa, and find out they all just needed to be cherished and respected. In the end the Simpson family escapes alive and unharmed, though their helicopter is being flown by pterodactyl Agnes.
