In the years between Ghostbusters (1984) and this film, The Real Ghostbusters (1986) introduced the idea that Slimer was living at the firehouse as the Ghostbusters' pet. Because the original film and the cartoon series were so popular with children, they put Slimer in the film.
While the role of Vigo was played by Wilhelm von Homburg, all his lines were dubbed by Max von Sydow. Wilhelm left the premiere in anger when he found out.
The yellow gadgets on the Ghostbusters' belts are "PASS Devices", real safety devices used by firefighters all over the world at the time of this production. The device emits a loud alarm if it doesn't detect movement after a predetermined time, for example if a firefighter is knocked unconscious or trapped. They have since been incorporated into the self-contained breathing apparatus worn by firefighters, and may include thermal sensors which sound an alarm when temperatures rise rapidly.
The kid who tells Ray that, according to his dad, the Ghostbusters are "full of crap" is played by Jason Reitman, son of director Ivan Reitman, and future Oscar-nominated director of Juno (2007), Up in the Air (2009), and Ghostbusters: Afterlife (2021). Reitman's daughter Catherine Reitman plays the girl with the puppy in Egon's lab.
Several factors contributed to the five-year gap between the original and the sequel. Bill Murray was on an extended sabbatical from acting, and was angered by new Columbia head David Puttnam calling him "an actor who makes millions off movies but gives nothing back to his art" at a British-American Chamber of Commerce luncheon. Puttnam also resented the blockbuster films, like the original, that his studio hit big with in the 1980s. When Puttnam was fired in fall 1987, his replacement, Dawn Steel, made a Ghostbusters (1984) sequel a priority. Michael Ovitz, who represented Bill Murray, Harold Ramis, and Ivan Reitman at Creative Artists Agency, arranged a meeting in early 1988 to smooth tensions and reservations that the four men had had in the ensuing years after the original's success. Ovitz's conflict resolution tactic worked, and production commenced shortly after the end of the 1988 Writer's Guild of America strike.
Ben Stein: One of the city officials who mentions the slime shell around the museum in the meeting at City Hall.