To start with fifty lives, highlight "Erase Game" on the main menu, and press B, A, R, R, A, L. Keep in mind you must use the Classic Controller to do this.
Blast through mine cart carnage
Near the begining jump over the cannon and fall next to the wall underneath. You should get blasted out of a cannon and sent in a cart almost all the way to the end of the level.
Infinite Bananas
In Bouncy Bonanza, after you obtain the frog, you will continuously be brought down this small path. If you jump up, you will get three bananas. Now, enter the cave where you got the frog, and you will fall down again. The same three bananas are there! That means you can do this forever and you will get infinite bananas.
Jump in mid-air
This works in the stage, "Mine Cart Carnage". Hit the Star Barrel in the level, and then either die or pause and press "Select". Enter the stage again. When the Star Barrel explodes, press Y and B simultaneously. You should now be jumping in the air, keep jumping by pressing Y and B in succession. You can use this glitch to jump all the way to the end of the stage.
Music Test
To access the in-game Music Test, highlight "Erase Game" on the main menu, and press Down, A, R, B ,Y, Down, A, Y, and Select. Keep in mind you must use the Classic Controller to do this.
Practice Bonus Rounds
To access Practice Bonus Rounds, press the following button combination during the intro on the Classic Controller: Down, Y, Down, Down, Y.
Secret Ending
Do everything in the game to achieve 101%. Win every level, every bonus level, secret bonus level, defeat final Boss.
Shortcut in Mine Cart Run
As soon as you begin the mine cart mission do not speed up but drop directly off the first jump and you will fall into a barrel which will then shoot you to the near end of the mission.
Unlimited lives
To make this work you must use a save game.On your last life die as Diddy Kong.Then press start at the "Game Over" screen. When Cranky Kong appears press Down, Y, Down, Down, Y. You will be brought to a room with 3 of each golden animal. You can enter any of these bonus games as often as you like. To exit, just press start, then select. You will be brought back to the last place you died in your save game.
Warp past Stop and Go Station
As soon as you start the level, walk left back into the entrance. You will warp to the end of the stage, where some manuevering will get you past the level.