Enter a level with Yoshi, Cape Mario, and a Fire Flower in reserve. Position yourself under a berry so you can get the fire flower and get the berry at the same time. If you happen to eat the flower and the berry at the same time, the game will freeze. Several things have been reported while using this glitch. Sometimes when the game freezes, your coin count will rise until you quickly have 99 lives. Press START and SELECT to exit the level. On another occasion the game froze, horizontal lines appeared on the screen, and strange music kept looping over and over again. Then came a buzzing noise, and he was returned to the file select screen, with his file deleted. Thankfully, that's not normal. Even so, this is an interesting glitch to exploit every once in a while.
Find a switch ( the kind that changes the square outlines into brown blocks) and be on a yoshi. Normally when you hit the switch, it will flatten and disappear. When you jump on it, quicky turn around and eat it with your yoshi, if you do it fast enough, you will have it in the Yoshi's mouth. You can spit it out and use it again.
Complete a stage with your time ending in the same digit repeated twice as the tens place of your Star total, and you'll be awarded an extra life. For instance, with 17 stars, beat the stage with your time ending in 11.