Yoshi's Story cheats and cheat codes for Nintendo 64

Stage select display
Hit C-Right or C-Left to turn the display, or hit Z or R to
adjust the zoom. 

Restart level
During gameplay, hit Z + L + A + B.

Mario Paint theme song
Listen to the game theme times at the "Time Trial" menu.

Purple Yoshi
Find all the coins from every stage.

Inifnite continues
If you lose your last life, hit the reset button on the 
Nintendo 64 system. You can begin the game from the last page.

Select Yoshi's color in practice mode
Go to "Trial" mode and choose any course. Select Yoshi color 
and hit Start, after hit Start + Z. Press B and begin practice
mode.