Different Endings
Beat the game as noted to unlock different endings (they will be available on the "Story Select" menu):
Audio Room - Finish Will's story.
Sketchbook - Finish Helen's story.
Helen's Video Room - Finish Helen's story with a least a C rating on all missions.
Will's Video Room - Finish Will's story with a least a C rating on all missions.
Unlock original "NiGHTS into Dreams" characters
Claris Sinclair - Obtain all 60 dream drops and jump into the fountain in the dream world with Helen.
Elliot Edwards - Obtain all 60 dream drops and jump into the fountain in the dream world with Will.
Easter Eggs: Halloween and Christmas
On Halloween (October 31st) most of the Nightopians in the My Dream garder will be wearing black witch hats.
On Christmas Eve (December 24) go to My Dream and you will hear the Jingle Bells song from Christmas NIGHTS playing in the background.