Two complex sequences were scripted for the game, but both ended up cut for different reasons. One would've involved Curtis escaping from the mental hospital and the other would've involved Curtis swimming in a river in the alien world. The game developers lost access to the filming location where the chase sequence was going to be shot, and had no backup, so the scene got cut. The river scene was cut due to space limitations on the fifth disc and was never produced.
Don Berg (who played Bob) admitted in an interview his character was originally scripted to have more interaction with the other characters, including a scene where he's sucking up to his boss, but these were trimmed from the script before filming began.
The Hectacomb was supposed to make a secret appearance in the crowd watching Curtis and Therese having sex for the second time at the club, but there was a technical problem on the day of shooting that prevented his appearance.
Except the game genre, the actress V. Joy Lee and one of the Easter Eggs - the promotion postcard for Adrienne Delaney's new book which Curtis receives in Chapter 3 - this game has little to do with the first Phantasmagoria (1995).
The trivia item below may give away important plot points.
It's never shown how Jocilyn knows everything at the very end of the game. A scene scripted but never in the game showed Jocilyn was watching the conversation Curtis had with Warner and saw what happened afterwards from outside the room through a window.