Ignore any other Baby Bowser role playing cheats, this one is a lot easier. First face Baby Bowser, but when the final bob-bomb hits, press reset 3 times very quick. On the Trial's Yoshi select screen, you'll only see baby bowser. (this only works if you have all 4 extra yoshis; Black, White, Boshi, Purple/ they do exist.)
Press C-Left or C-Right to turn the display, or press R or Z to adjust the zoom.
If Yoshi is low on eggs, is not next to a egg block, and super happy, prepare to fire an egg but cancel that action. Yoshi will put the egg into the inventory and allowing it to be kept.
Mario Paint theme song:
Enter the "Time Trial" menu and listed to the game theme eight times.
Shrink in "Piranha Groove" (level 4-4). Hit an egg block while shrunk to create a very small egg. Take it while still shrunk. The egg will remain small as you return to normal size. Note: The mini-egg is still as powerful as the full-size version.
Locate and get a white Shy Guy. Complete the current level and enter the character selection screen for the next level. Select the Shy Guy to restore one of the dead Yoshis. Note: If no Yoshis have been lost, the white Shy Guy will not appear.
Select Yoshi's color in practice mode:
Select any course under "Trial" mode. Select the desired Yoshi and press Start, then press Start + Z. Press B and being practice mode with that color Yoshi.
Collect six melons in a row during a mini-game to get a heart fruit. Eat the fruit to create a letter made from coins at the end of the mini-game. If you use the letters in the order of appearance by level, they spell the following phrase: "YOU ARE YOSHI'S GREAT PARTNER".