Road Runners Death Valley Rally (SNES)

Ninety-nine lives:
Press Select at the title screen to display the options screen. Then, press A, Y, A, Y, X, Y, B, A, R, L.

Seventy-five lives:
Hold L + Right + Y + Select and press Start at the title screen. Continue holding Start until the text "Zippity Splat" appears on top of the screen.