Hi-rez mode:
Press C-Left(2), Left, L(2) at the title screen. Note: An expansion pak is required.

No damage or failures:
Press L, Z, Start, Up(2) at the title screen.

Bouncy cars:
Press C-Up, C-Left, R, Up, Left at the title screen.

100,000 sponsor credits in support van:
Press L, Z, Start, L(2) at the title screen.

Max championship points in support van:
Press L, C-Up, Left, L(2) at the title screen.

Fat world:
Press Z, C-Right, L, Up, Right at the title screen.

Thin world:
Press Z, C-Right, R, Up, Right at the title screen.

Upside down world:
Press C-Up, Z, Start, Up, Down at the title screen.

Volcano valley world:
Press C-Left, Z, R, L, Down at the title screen.

Large tire:
Press C-Left, Z, R, Down(2) at the title screen.

Wobbly tire:
Press R, C-Right, Start, Down, Z at the title screen.

Repair power:
Press L, Z, R, L, Start at the race description screen

Speed warp view:
Press Z, C-Left, R, Up, Right at the title screen.

Speed-based aspect ratio:
Press Z, C-Left, L, Up, Right at the title screen.