All Cars, Tracks and Difficulties:

At the Mode Select screen, press L, Z, R,C-UP, C-DOWN, C-LEFT, C-RIGHT,
START. You should hear a chime if you did it correcly. 

------------------------------------------------------------------------
Change Car Colors:

To change your car's colors, simply press the R-Button during the car
customization screen. Note that there are only a few select colors for
each vehicle. 

------------------------------------------------------------------------
Joker Cup:

To get the Joker Cup and six additional tracks beat the Jack, Queen,
and King Cup on Standard difficulty. 

------------------------------------------------------------------------
Mute City II Shortcut:

Right after you make the third hard turn, you will see a ramp to the
left that looks like it will lead you off track. If you hit it with a
booster, you will fly over the gap and onto the next strip of tracks. 

------------------------------------------------------------------------
Rotate Cars on Customization Screen:

Want to see your car from different angles? At the customization screen
press the C-Buttons to rotate the car in all directions. 

------------------------------------------------------------------------
Smaller Cars:

At the car select screen press and hold the (L) and (R) buttons. While
holding those buttons press C-LEFT and C-DOWN to shrink the cars. 

------------------------------------------------------------------------
Title Screen Changes:

To have the title screen change to a comic book motif, beat F-Zero X on
Expert. For a second change, beat the game on Master difficulty. 

------------------------------------------------------------------------
X-Cup (Track Generator):

Beat all four cups on Expert difficulty to open F-Zero's hidden X-Cup.
This cup will randomly generate six courses, ranging from utterly
boring to plain cool. Beating the four cups will also open a Master
Difficulty level.