Deleted Scene: One such scene in the second movie helped explain the moment when Vigo possesses Ray during the final showdown. During the first museum visit, the guys examine the painting of Vigo and fans may remember Ray being hypnotized and needing to be snapped back to reality. This was supposed to lead into a sequence where Vigo tries to use Ray to crash Ecto-1 and kill the Ghostbusters in a traffic accident. Winston manages to grab the wheel and save the day, while Ray - no longer under Vigo's influence - can't account for what just happened. Note that a couple of clips from this sequence were used in the montage - specifically Ecto-1 crossing through an intersection and Peter in the car, looking bewildered.
Genius Bonus: Probably unintentional, but "Zu ul" is actually a plausible Sumerian noun phrase, meaning "Ancient wisdom!"
Hey, It's That Guy!: Bill Murray's brother Brian Doyle-Murray has a cameo as the psychiatrist in the second film. (Point of fact Brian has a bit part in a lot of little brother Bill's movies.) He is also the voice of the mayor in the 2009 video game (see Hey, It's That Voice! below).
Ben Stein has a bit part in the second film when the mayor decides to call in the Ghostbusters.
Cheech Marin is a dock worker in the second film who witnesses the arrival of the Titanic and says, "Well, better late than never!"
And Max von Sydow is the voice of Vigo in the second film as well as the game.
And Alyssa Milano is Dr. Ilyssa Selwyn in the game.
And Peter MacNicol, who portrayed Janosz in II is also the voice of the Mad Hatter.
What Could Have Been: For a great movie, Ghostbusters varies tremendously from its original concept. Aykroyd's original script called for multiple groups of ghostbusters who traveled through time and fought ghosts in different dimensions. This idea was rejected as technically unfeasible in 1985; supposedly, the special effects would have cost over $300 million. Ivan Reitman re-purposed the script as a "going into business" story to make it more accessible to audiences.
Many actors were switched out or not intended as their original performers.
The part of Venkman for written for John Belushi, but alas.... Bill Murray, the driving force of the movie, was a last-minute addition to the cast. While Murray made the role his own, several lines are clearly intended for Belushi, such as the speech after the university fires them. It sounds corny from Murray, who usually plays a cynic, but Belushi was good with such speeches.
Eddie Murphy was to play Winston, who would have been part of the original group along with Ray, Peter and Egon. He was described as a former Marine and Ph.D.-level scientist, the original script called for Winston, not Venkman, to be slimed in the Sedgewick Hotel. Murphy was left out because they didn't want the movie to be perceived as an SNL-inspired film, and because he was busy with Beverly Hills Cop at the time.
The part of Louis Tully was initially offered to John Candy, who wanted to play him as an odd German guy who owned dogs. The directors didn't like this idea, since there was already so much dog imagery in the movie, but couldn't bring themselves to replace him. Fortunately, Candy passed on the role, and they offered it to Rick Moranis, who had a much better take on the character. It helped, too, that Moranis, Candy, and Ramis were all friends since Second City together, and understood that the best guy for the role was the best guy for the role.
Harold Ramis was not originally intending to play Egon, he never had much success as an actor and was just interested in writing for the film. After a hard time casting for Egon, Aykroyd and Reitman suggested that Ramis would be perfect for the role and as soon as he read for it everyone agreed.
The Stay-Puft Marshmallow Man was on the chopping block. The producers were worried that audiences wouldn't buy the character, and were prepared to produce a different ending if test audiences didn't react positively. Fortunately, they did, even though the test version of the movie lacked completed special effects, making him more of an Ultimate Evil.
The second movie was apparently supposed to start getting into the "other dimension" aspect of the mythology but that was changed at the last minute to something closer in plot to the first movie. Bill Murray was upset with the radical changes to the script and it is another reason why the third movie has been in Development Hell. Unfortunately, it is this similarity to the first movie that contributes to its overall poor reception. The Game was able to finally get into this aspect of the premise, being cheaper to do than a movie format.
Originally Gozer was going to take the form of a man in a business suit and would have been played by Paul Reubens. Reitman was the one to devise the androgynous form at the last minute, believing it would work better as a supernatural manifestation rather than the rather mundane look. However, the Video Game's design of Ivo Shandor is said to be based upon what Paul Reubens might look like in ten or fifteen years' time.