Intrusion of the POD-Y snatchers, seems to be an allusion to the Invasion of the Body Snatchers (1956) which in turn is based on The Thing from Another World (1951) (as Comic Book Guy attempted to say before being devoured).
On a map consulted by Lisa, there is an island called "Margaritaville", that is song written and performed by Jimmy Buffett .
Lisa consulted a map which contained Skull Island. That is the home of King Kong as illustrated in the film Kong: Skull Island (2017) .
Cthulhu is a reference to an entity from the works of American Science Fiction author H.P. Lovecraft .