Julia Montgomery refused to reprise her role as Betty because in the original script Betty is caught cheating on Lewis. Montgomery felt it betrayed the change in her character from the first film. Joe Roth offered to have the scene re-written but Montgomery still refused. She eventually returned for the following sequels. Lewis is shown packing a picture of Betty in the beginning of the film, implying they're together and that Lewis cheats on Betty with Sunny later in the film.
MTV ran a promotion called the MTV Body Snatchers involving the Beastie Boys where one of the prizes was to be an extra in this movie.
Anthony Edwards did not want to appear in the sequel due to a combination of feeling the original had told a complete story, not wanting to be pigeon-holed in goofy comedies, and simply not liking the script. While contractually obligated to appear here, the producer and director adjusted the script so that Edwards was able to film his role quickly and in a limited space - either for the scenes where Gilbert is at home in a wheelchair after breaking his leg or for a dream sequence in which his image was put into a scene via special effects. In the following sequel, Edwards is replaced by Mike Greenwood, while the character is absent entirely in the final installment of the series.
Actress Theresa Lynn told Draculina magazine that she filmed a nude scene, but it was cut out when they decided to go with a PG-13 rating. She had no idea that happened until she took several friends to see it and her part never came up. She said it was very disappointing, especially since she had helped three of her friends get cast after she was and their parts stayed in.
After this film, Bradley Whitford was often cast as villainous characters to the point of being typecast. This went on for over a decade until Whitford was cast as the opposite in The West Wing.