Bill Murray (Peter Venkman)
Fun fact: The role of Peter Venkman was originally written for John Belushi before his untimely demise. Other actors were up for the role before Murray landed it, yet, to contradict popular belief, Michael Keaton was not in fact one of those that turned the role down.
Dan Aykroyd (Raymond Stantz)
Fun fact: The title of the original draft of the film — which was written and conceived by Aykroyd — was Ghost Smashers.
Ernie Hudson (Winston Zeddemore)
Fun fact: Hudson was a single father raising his sons in Los Angeles' Laurel Canyon when he got the part. Not-so-fun fact: Hudson lost the role of voicing Winston in the animated The Real Ghostbusters, with the role going to Arsenio Hall.
Sigourney Weaver (Dana Barrett)
Fun fact: When possessed by the demon spirit of Zuul, Weaver's voice was actually dubbed by director Ivan Reitman.
Rick Moranis (Louis Tully)
Fun fact: The role of Louis was originally offered to John Candy, who turned it down, with the part eventually going to Moranis. Also, almost the entire "OK, who brought the dog?" party scene was improvised.
Annie Potts (Janine Melnitz)
Fun fact: According to Potts, in her mind the character of Janine now runs a pest control company and lives with 17 cats on the Jersey Shore.
Harold Ramis, who played Egon Spengler, was omitted due to his death earlier this year.