Hey Bob I decompiled the function CheckNames and figured out what the "MR DULL" cheat does that you were asking about earlier. This is what your name is automatically changed to when you enter an empty player name. In the international release of the game it will also convert the palette to grayscale. The palette swap seems to have been disabled for the US release but the name change is still present.

There is also another cheat that was removed. It looks like during development you could enter "CLONES" as your name and it would allow any number of players to pick the same car in network multiplayer mode. This has been completely removed in both US and international released and doesn't even update the player name when entered.

You can also enter "PROCESS" and it looks like it detects differences in floating point math processing.