Cole looks significantly older than in the original (even though the events take place two years later). This is because even though the original was released in 2017, The Babysitter (2017) was filmed in 2015, The Babysitter: Killer Queen (2020) was filmed in late 2019.
When Phoebe gets out of the 18-wheeler at the lake, she mentions "Large Marge". That's a tribute to Pee-wee's Big Adventure (1985)'s ghostly truck driver, Large Marge.
Shot from October 14, 2019 - November 24, 2019 (41 days).
There are two Star Trek references: when Phoebe is going through her 'flip book' in class, it says "Star Trek: Picard (2020) Picard 1- 0 Alien." Later when John is taking to Melanie on the dock, the boat behind him says "Spock."
When Phoebe first shows up in class, she mentions that her favorite film "vacillates between Deliverance (1972), or anything by Rob Reiner". Later, when she and Cole escape the party boat and wind up back on shore, she wanders into the campsite of a sketchy redneck camper playing the plucky opening strains of "Dueling Banjos" (from Deliverance (1972)). When he starts to get grabby with Phoebe, Cole suddenly pops up next to them, asking if they're making s'mores (and frantically expounding on how to make the perfect s'more) - he caps this by declaring, "I eat them just for PLEEEEAAASSSUUURE!" This is clearly an homage to a scene in The Sure Thing (1985) (directed by Rob Reiner), where the character Gib saves his traveling companion Alison from a handsy cowboy she's hitching a ride with - Gib pretends to be a psychotic hitchhiker who could potentially "rip your heart out and eat it, just for PLEEEEAAASSSUUURE!"