Play as Luigi:

Who says Luigi is overlooked? The man in green made it into super Mario brothers deluxe for game boy color, and you can replace Mario with him by pressing the select button while viewing the map screen in the original 1985 and challenge modes only.

Super Players:

Go to level 5-1. At the very beginning, there will be a turtle. Jump on him to stun him then kick him forward. Run after him holding the b button and forward. Once he kills everybody you will get a one-up. After that, kill yourself and repeat the steps until you get 300,000 points. After you lose all your lives, rank in and return to the main menu. There will be a Luigi head. Select it and you will have Super Mario for super players!

The Great You vs Boo:

If you are not good enough at this game to get 100000 points or more, but you can make it to world 5-1, try this: Go to world 5-1. The first baddie you will see will be a Koopa Troopa (Turtle). Jump on it. Kick it forward. Immediately run after it while holding the B button. After it kills everything, you will get a 1UP. Let the turtle kill you and repeat this until you get 100000 or more points. Keep killing yourself until you lose all your lives. YOU MUST RANK IN! Go back to the Main Menu. See a new icon? Select it to get You vs Boo option!

Fire Power Against Boo:

Once you have accessed "You VS Boo", click on Boo. In the screen where you choose a level press, Select. Mario will turn into Super Mario. Press select again and he will turn into Fiery Mario do it again and he will turn into regular Mario.
Note*: This also works in VS mode against a friend.

127 "1 up's!":

On world 3-1, as you are going up the steps to complete the board, stomp on the 2nd turtle and repetitively stomp him into the staircase 127 free guys will be added to your life count. *Note: If anyone remembers Super Mario Bros. on the first Nintendo, this is the same as the "50-men" trick.