At the level select screen, hold SELECT and press L, L, B, A, R to unlock bonus games.
Unlock New Levels
Beat the game and unlock 6 new levels.
Get Hard Mode
If you get 1000 points in a world a star will appear on the 'Select Game' screen. Once 5 stars are earned it unlocks Hard Mode.
Get Secret Ending
If you get 1000 points in a world a star will appear on the 'Select Game' screen. Once 6 stars are earned it unlocks a secret ending.
Get Bonus Endings
Bonus 1: Complete all the levels in a world, EX. complete the levels for world 1 1-8 with 100 points [30 points for stars, 20 points for the red coins and 50 points for all 5 flowersand get bonus 1
Bonus: Beat bowser on level 6-8 and all of the bonus 2's open on the all of the worlds Final Ending: Beat the game with 1000 points and that includes the bonuses
Note: you can't get the final ending just by getting all of the points, you must fight Bowser again to give you the final ending.
If you get a world score of 777 you will get 7 lives.