A somewhat old discovery that wasn't documented all that well until a few months ago. To start debug mode, type 'ogel' while playing. The following keys will then have the following effects:
A: Loads Information Center cutscene
C: Press C and a number at the same time to view a location for a single frame:
C + 0: Race Track
C + 1: Hospital
C + 2: Jail
C + 3: Near Post Office
C + 4: Inside Pizzaria
C + 5: In front of mountain, in Race Track area
C + 6: Inside Police Station
(These sometimes do other stuff, like loading seemingly random cutscenes, like the ending videos)
D: Viewpoint is lowered
F: Switches model quality to low
G: Press G and a number at the same time for the following effects:
G + 2: Brickster escapes
G + 3: Loads Helicopter minigame
G + 4: Plays ending cutscene (Pepper wins)
G + 5: Plays ending cutscene (Brickster wins)
H: Switches model quality to high
L: Press L and a number at the same time for the following effects:
L + 0: Changes lighting
L + 1: Changes lighting
N: Locks frame in place until N is hit again
P: Disables flowers, trees, etc
S: Stops music - Press again and then load new scene to undo
U: Viewpoint is raised
X: Switches model quality to normal
Tab: Shows framerate counter
In addition, messing with - and + on the numpad while playing can have some pretty strange results, like teleporting the player a point little bit forward and up from the current position, or teleporting another character to that point. The results can be quite funny sometimes. Hey Wes, can you tell us anything about this stuff? Like what it was originally intended for?