In the first level of Forest of Illusions, get through the level until you reach the halfway point. Then get a Super Star from the box of random iteams. Then, go through all of the Red Koopas while you have the Super Star's power. If you get through ALL of the Red Koopas before the Super Star's power wears off, you will get a maximum amount of 11 lives! Keep repeating this process until you have maxed out your lives!