You can get up to 5 stars, which will help allow you to unlock Hard Mode.
At the end of ShadowMan's level (the Mother Computer), on the right there is the Gamecube Logo.
When fighting Thunderman, when one of the clouds is about to move on a pannel near you (when it's about half way on), move onto the same pannel. The game recognizes it as hit, but you don't take damage. If done right, you should have the Invis chip effect for about 1/4 of normal time. This is a useful trick for S ranking him.
Requirements:
2 GBA/SP
2 MMBN2 game paks.
Link cable
This glitch allows you to duplicate your lost chipdata in a netbattle against your oppenant, do not worry about it damaging your gamesave, I have done this hundreds of times and my gamesave has not suffered.
You and your friend (or just you on your own, still possible to do) must go into network and compete in a real netbattle against eachother, and one must win without flaw, when the battle is over, as soon as the chip datas name is shown, the LOSER must reset his game. (A+B+Start+Select), as a result, where the winners data is saved and the losers is not, the losers chip data is not lost and the winners is still saved resulting in a duplication of the chip.
WARNING: If the winner resets, instead of duplication you will simply DESTROY the chip, because the loser still loses and the winner doesn't save the fact it was won.
What are the benefits to this? Well in short, imagine how easy it'll be to duplicate and share your secret chips, Bass V3s, Lifeaur3s and other rare only get one of me chip data. You can even duplicate the final chip data, Sanctuary. Of course the better the busting level, the better the chip you'll duplicate.