Trivia: Director Jason Reitman is the son of Ivan Reitman, director of the original "Ghostbusters" and "Ghostbusters II." As a child, Jason actually had a cameo in "Ghostbusters II" during the birthday party in the beginning. (He's the kid who tells Ray he heard the Ghostbusters were "full of crap").
Trivia: The same advertisement for Stay-Puft Marshmallows in the original movie is visible on the side of one of the buildings in the town. It's in roughly the same shape as the billboard in the 1984 film.
Trivia: Spoiler! Stay for an additional scene with Annie Potts and Ernie Hudson in his office talking about the old days and even though he is a businessman how he would always be Ghostbuster.
Trivia: There is an extra scene with Bill Murray and Sigourney Weaver after the credits roll. She is testing his psychic abilities with cards.
Trivia: Part of the reason a third "Ghostbusters" movie wasn't made in the 90's or 2000's was because Bill Murray didn't really want to return to his role of Peter Venkman. It was even rumored that Murray would immediately shred any "Ghostbusters 3" scripts that were sent to him. After many months of speculation, it was finally reported that Murray agreed to reprise the role in this film, alongside many other original cast members.
Trivia: If one counts his cameo in the 90's film version of "Casper," this will actually be the fourth film to feature Dan Aykroyd as the character Ray Stanz.
Trivia: Originally, sequels were planned for the 2016 "Ghostbusters" reboot. However, when the film attracted some controversy and fell short at the box office, plans for the sequels were abandoned. Eventually, an idea was hatched for a direct sequel to the original two films, which became "Ghostbusters: Afterlife."
Trivia: Finn Wolfhard appears as a main character. He's also the star of the popular Netflix series "Stranger Things." Ironically, in an episode of that series, his character wore a "Ghostbusters" outfit for Halloween.
Trivia: Set to be released 31 years after the release of "Ghostbusters II" and 36 years after the original film.
Trivia: The clerk at the hardware store is played by Tracy Letts, who is Carrie Coon's husband in real life.
Trivia: Gozer is actually played by three different actresses. Shohreh Aghdashloo provides Gozer's voice. Emma Portner portrays the spectral version of Gozer that appears when Gozer is not "whole." And an uncredited Olivia Wilde plays Gozer in its "human form" in a cameo appearance.
Trivia: This is the first Ghostbusters movie not to have a Slimer appearance.
Trivia: The giant eyeball ghost was modeled after a toy that was released for the 1987 cartoon.
Trivia: SOME SPOILERS: Harold Ramis' daughter Violet got to visit the production a few times, and was even able to try on her father's original proton pack, which was being kept in storage. She has greatly praised the movie and the effects used to add her father into the film as a ghost, and feels he would have definitely approved of it.
Answer: Yes, it is still canon. Director Jason Reitman has confirmed it is, and there are actually lots of easter eggs referencing it in "Afterlife." For example, Ray still has his bookstore from "Ghostbusters II." The "dancing toaster" is in the farmhouse. Etc. They chose not to directly reference it in dialogue since it didn't have much to do with the plot, but there are plenty of hidden details confirming it is still canon. Reitman has also said that there are plans to possibly bring back more plot/characters from "Ghostbusters II" in the future. (It just depends on what direction the sequel ends up going in).
TedStixon