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."
Melanie says to Cole "It's red pill or blue pill time"', a reference to The Matrix (1999), where taking a blue pill will keep the user trapped inside the Matrix, whereas the red pill enables them to be freed from it. Cole then steps outside the classroom, and has the choice between a blue hallway that leads further into school, or a red hallway that leads outside, to join Melanie and skip school. Also, Samara Weaving's uncle, Hugo Weaving, famously played Agent Smith in The Matrix.