Normally in a level, a moustached player can brake a box and there will be a mushroom inside. Try this with Yoshi however, and he'll not be able to break it, therefore not getting the mushroom and not growing big. Solution!

1. Start level as yoshi
2. Get a cap
3. Make sure an enemy is close to the mushroom box
4. Break the box
5. Get ingured by the enemy
6. You'll lose your hat and return to yoshi.now grab the mushroom before it's gone!