Hold Select, press L, L, B, A, R (on stage select screen)

Simply beat the game 100% and the next time you boot up yoshi's island the game's title screen will show yoshi's island but it will be night instead of day

Collect a certain amount of points in a world to get a special surprise. (Note: the first three apply for all 6 Worlds.)

Score 1000 World Score Points and get 5 additional stars

Get your total points for a world to equal to exactly 777, to get 7 extra lives.

To get the new ending complete all 60 levels with 100 points (total of 6000 points which make 6 stars on the Title screen and Select game screen) and shows how many times you played on any level..

After you have gone over all the hills there is a pipe that Shy Guys come out of. Ignore them and go past the pipe and get rid of the Killer Plants in the next two pipes to the right (one above and on the ground). A Kooper is walking between the two pipes on the ground. Jump on the Kooper and send his shell spinning between the two pipes. Shy Guys continue to jump out of the pipe on the left and every time the Kooper shell hits them you will hear a different sound that means youre getting lives! Stand on the pipe on the right and the lives will continue for as long as you stay on this screen.

Pick up a Rollie-Pollie Guy with your tounge. Do not turn him into an egg or spit him out for anyone until you get to the pipe that spits out Shy-Guys. Once there, spit the Rollie-Pollie Guy out into a 1 (square) hole on the right of the pipe. Once placed, jump onto the platform above and to the right of it. Let the Shy-Guys jump out of the pipe and onto the Rollie-Pollie Guy. Points will accumulate and will eventually give you 1-Ups continually. After a few hours, you will have 999 lives.

To get special Yoshi eggs with out having to find special boxes, fire a Yoshi egg in an area that will cause the egg to bounce off the walls and back to you. When the egg returns to you, quickly use Yoshis tongue at the egg. If successful, you should have a special Yoshi egg.

Go to any level with lava. Fall in the lava near land and you will fall through the ground.

Go to a place where there is shallow water. Get high up, then Ground Pound into the water. If you hit it correctly, you will not swim in the water, but instead walk. You can also spit seeds, throw eggs, and crouch.

Grab a Melon Bug (the creature that rolls up into a ball) and go to the pipe with Shy Guys jumping out of it. Spit the Melon Bug close to the pipe on the left-hand side. When Shy Guys jump out, after a while you will get a "1-Up" for each time a Shy Guy hits the Melon Bug when it is in its melon form.