Throwing the Boomerang and holding the button the Boomerang is on will put Link in a strange state. In this state, you won't be able to move Link yourself and his height value can't be changed. Since his height value can't be changed, you can do some interesting things by using the Down Thrust and Bombs. For example, you can clip into certain doorways:
It is possible to spawn the Boomerang at the top left(?) corner of the screen by throwing the Boomerang right after using the Lantern. Using this, Link can remain in the state for a much longer time. Jumping into a whirlwind and holding the button the Boomerang is on when Link is about to land (you can also press R to jump down immediately) will cause Link to float in the air until the Boomerang comes back to him or until you stop holding the button.