XTreme Racing

On the 1st selection screen type any of the following:

   SHEEPY SHEEPY          For a sheep as a vehicle.
   XR3ITURBONUTTERBASTARD For a faster engine?
   IDKFA                  For auto qualify.
                          (and access to 3 bonus tracks in single track mode)

HINTS:

Grassland 1 has a short cut - where you have the blocks in the middle
of the road.  Go just past there and you can drive through a tree.