I've played this game reasonably thoroughly and decided to look up the requirements for 100%. I was shocked to see the sobering accomplishments that must be done. Caution: there is one spoiler (hint: if you played galaxy 1, it's no big deal.) I try to find things out for myself in games, but I'm glad I researched before I went deeper into attempting to reach 100%. Warning: Spoilers inside! You must beat ALL LEVELS with BOTH Mario and Luigi. Damn. You must get golden flags on every level. Edited, there is indication, just get them all on the Luigi run, like I will do.