Attack With Hat
In the second snow land, go to the big snowman's head and get your hat blown off. Go to the warp trees and warp back and forth about 10 times and go back to your hat. There will be 11 hats, but only pick up one, then all the rest.
(Thanks to ratstail@email.msn)

Big Boo Giggles
Walk up the winding stairs, and come back down and go to the first snowman's land painting room and go down the right ramp.
(Thanks to ratstail@email.msn)

Bowser 1-Up Loop
When fighting Bowser, collect 100 coins from his breath of fire. If you lose a life, but get 100 coins first, you'll gain a life. Must be done on final Bowser.
(Thanks to Remy86@aol.com)

Bowser -120 Stars Message
Bowser's message will be different when you fight him after getting 120 stars.
(Thanks to SEAN712@aol.com and others)

Cinema Camera Change
When you beat Bowser, have a second controller plugged in, and you can alter the ending camera angles with the analog stick.
(Thanks to SEAN712@aol.com and others)

Extra Life
If you jump on 6 Moles in any level with moles, you’ll receive an extra life.
(Thanks to toadstool83@hotmail.com)

Extra Lives
Talk to Yoshi.
(Thanks to Conman9515@aol.com)

Extra Lives in Ice Stage
Begin your slide on the first Ice Stage. When you reach the first left turn, aim for the row of Coins and you'll slide into a tunnel that holds 2 extra lives.
(Thanks to toadstool83@hotmail.com)

GameShark Glitch
Turn on "Walk Up Hills" (it should be built into the GS, then play the game. Drain the moat. Go into the invisible Mario hat switch palace (the hole in the ground), then jump off the edge. You'll be swimming in the air (no water) where the moat was.
(Thanks to Conman9515@aol.com)

Go Through Bridge
Go under the bridge in the first course, and press and hold A. Release the A button when you're at the lowest part of the bridge.
(Thanks to Remy86@aol.com)

Hidden Coins
Run around a post in any level five times, for hidden coins to appear.
(Thanks to toadstool83@hotmail.com)

Hidden Room
Get 120 stars, go to the roof, get a winged hat, go back to the cannon, shoot to the cloud above the middle tower, and walk to the left side of it when you get there. You'll fall in a strange room.
(Thanks to Remy86@aol.com)

Infinite Lives Against Bowser
Get a 1-Up by walking behind the top left pillar against the final Bowser.
(Thanks to Remy86@aol.com)

Li'l Penguin Imitates Mario
On the first snow level, get near the li'l penguin and run and slide on your stomach.
(Thanks to Remy86@aol.com)

Mario Sparkles
After talking to Yoshi, doing three jumps and falling from high heights will not hurt you, but it will make you sparkle.
(Thanks to Remy86@aol.com)

Race Larger Penguin
Go back to Course 4, select Big Penguin Race, and race a much larger penguin.
(Thanks to Remy86@aol.com)

Second Snowland
On the 2nd floor, go into the portrait and mirror room. Look in the left side of the mirror. It's the Snowland portrait but it’s not on the wall. Jump into the wall where the mirror shows the portrait.
(Thanks to Vegeto1991@aol.com)

Stolen Hat
In Snowman's Land, lose your hat, and save the game (without picking up the hat). After turning the game off and then on again, re-enter the level, and you'll see one of the snowmen wearing the hat.
(Thanks to Remy86@aol.com)

Tick Tock Clock
Depending on when you enter Tick Tock Clock, the gears and gadgets will be altered. For example, enter it when the hand's on the 6 to make everything stop.
(Thanks to Remy86@aol.com)

X-Ray
Go through a door, and quickly turn around and go through it again, and stop. After a few attempts, you'll get an X-Ray of Mario.
(Thanks to Remy86@aol.com)

Yoshi
Get 120 stars, go to the cannon that appears outside the caslte, and shoot yourself to the roof.
(Thanks to Remy86@aol.com)