How to perform
When Kirby Inhales Yoshi and copies Egg Lay, and uses Egg Lay on Yoshi, Yoshi will shrink if he breaks out of the egg fast enough. The mashing requirements to break out fast enough for the glitch to occur is extremely high, and as such, the player may need the game to be slowed down to successfully perform the glitch, either by changing the game speed in Training Mode or playing in Slo-Mo Melee.
When Yoshi is KO'd, he'll return to normal size. He'll also return to normal size if Egg Lay is used on him and he does not break out fast enough for the glitch to occur.
Despite common belief, this glitch cannot be done with two Yoshis. It can only occur with Kirby using Egg Lay on Yoshi.