Alec and Lee's bedroom has a Ghostbusters poster on the wall.
Peter: "Go through the phone book, Slimer." You've been waiting all week to try that, haven't you?
Ray: Yeah! How did you know?
Peter: You had that look.
Peter: (seeing Slimer in his bed) There's no way I'm that tired. (small pause) Yes, I am.
In the book that Egon's looking through, you can see pictures of Drool the Dog-Faced Goblin (from "Drool The Dog-Faced Goblin") and the Bird of Kildarby (from "The Bird Of Kildarby").
Mrs. Faverhsam gets a mention in this episode. Since last we've seen her, she's apparently adopted a cat.
An episode of Extreme Ghostbusters, "Grundelesque", would be a follow up to this episode.
Nightmare On Elm Street 2:
The part where Alec is changing into The Grundel is just like the scene where Jesse is changing into Freddy Krueger and the background is like where Freddy is. Peter Venkman is talking Alec out of being The Grundel is just like Jesse's girlfriend is talking him out of Freddy to change back into Jesse. The outfit is like Freddy Kreuger's outfit throughout the films.
The tune that Ray, Peter and Winston whistle when they get back to firehouse after the school assembly is the Inspector Gadget theme, another show created by DIC.