This episode reveals that the Dinklebergs set their calendar 2 months ahead of everyone else. This is a reference to the canon episode "Operation Dinkleberg", where Timmy disguised as Santa visits the Dinklebergs and Sheldon asks him what he's doing here in September, even though the episode is set in July.
The Simpsons - This episode is similar to the Simpsons Halloween specials, titled "Treehouse of Horror", with the set-up being similar to "Treehouse of Horror III".
The Mayor of Dimmsdale saying that he welcomes their new alien overlords is a reference to the Simpsons episode "Deep Space Homer", where news reporter Kent Brockman says "And I, for one, welcome our new insect overlords" after having witnesses a close-up of an ant inside the Corvair space shuttle and coming to the conclusion that giant space ants have taken it over.
Fred Figglehorn - The movie that Crocker and Vicky forced the kids to watch and riff on in "Halloween Horror Theater 3000", titled "Sid: The Movie" is a parody of Fred: The Movie, Fred 2: Night of the Living Fred and Fred 3: Camp Fred, all of which have negative reception, and were released when Fred, a web show created by Lucas Cruikshank and the most popular channel on YouTube at the times of 2009-2012, was on Nickelodeon for a certain period of time, which got him his own show and 3 movies. The Fred expy is named Sid Smeckledorf, and is voiced by Dee Bradley Baker, poking fun at Fred Figglehorn's high voice.
Rocko's Modern Life - In addition to A.J.'s costume, the epilogue features Dinklebergs' home being overgrown with slime as a prank by Mr. Turner, who sent the Dinklebergs slime as "a Christmas present" and exploited the Dinklebergs' flaw with setting the time 2 months ahead on their calendars, similar to the ending of the Rocko's Modern Life episode/pilot "Trash-O-Madness", where Spunky dips the slime he found into Rocko's bathtub, thus making the slime overgrow Rocko's house.