Cheat mode:

Press [Shift] + [Ctrl] + ~ to display the console window. Type extract, press [Space], then press [Enter]. A file named "!!!Readme.txt" will be created in the game directory. Read the file on how to activate the various hidden features in the game. These include the extraction of multimedia files, activation of various secrets, and the creation of places and animations. To activate all the Easter Eggs, type Tippe: SetFlag("egg") at the console window.
Developer cameo:

Locate the bookstore window that has the book on the Holy Grail. Look in the window next to the door to see Jane Jensen, the woman that developed the Gabriel Knight series of games. Additionally, examine the book that Gabriel authored about the Voodoo Murders. Gabriel will say "Wow, isnt he some famous author or something?"