When getting a Big Egg (as in World 2-7), you can carry it to another level. Go to the Goal Ring and past it to the right side of the screen. Aim the Big Egg straight up, launch it, then lick it with your tongue; repeat as necessary until the Big Egg is launched to to the right and about half off-screen. Then enter the Goal Ring. The next Yoshi to come will pick up the Egg, carrying it with the others and Mario to the next level. Note that the Big Egg's graphics will glitch up, but it'll retain its normal functions.