This segment is a parody of the film Invasion of the Body Snatchers, and to a lesser extent, The Thing. This is pointed out by Comic Book Guy just before he dies.
During the spore-launching scene, the Planet Express is shown with a banner saying "Bring Back Futurama. It is then destroyed by the Orville from the Star Trek parody show The Orville. It also acts as a subtle reference to Matt Groening's rivalry with Seth MacFarlane, as the latter show was created by MacFarlane and starred him.
The hallucination dream that Lisa has is a reference to 2001: A Space Odyssey
During the hallucination, Homer and Bart's insult to Lisa for being a vegetarian from Lisa the Vegetarian makes an apperance, followed by Luci from Disenchantment making a brief appearance, showing him sitting on the Dreamland castle while smoking.
Bart and Lisa drive past Hollis Hurlbut in the police car, and he is doing the surprised face and pointing gesture that Donald Sutherland's character does in the 1978 version of Invasion of the Body Snatchers; Hollis was voiced by Sutherland.
This segment is a parody of the 2016 film Split and The Three Faces of Eve, while the title is a parody of Multiplity.
Lisa sings a song to the tune of "This Is It", the theme song for The Bugs Bunny Show.
The segment and its title are a parody of the Jurassic Park films.
The map on Lisa's iPad details various fictional islands, including Skull Island, the Island of Dr. Moreau, Gilligan's Island, Margaritaville, and the island from Lost.
A list of dinosaurs and reptiles featured in "Geriatric Park":
Unknown theropod resembling the Indominus rex
This is the first Treehouse of Horror episode to contain a SpongeBob reference in 8 years since "Treehouse of Horror XXI."
The last time Homer ignored a warning not to turn up a thermostat in a "Treehouse of Horror" episode was in the segment Nightmare on Evergreen Terrace from "Treehouse of Horror VI".