I've for the most part beaten the Wii and GC versions of Paper Mario. I can't beat either of the last bosses.On the Wii version I can beat the first boss, but not the second. I always get stuck in corners.
Sweet Kandi: I found the second boss on the Wii version easier than the second.
Blast him with loads of Bowsers Flame Breath while on the floor, then turn Peach and get to a high platform and bounce off Super Dimentio's head and neck area. When he attacks with missiles use Slim to turn invisible. If you are in a corner, just use the corner to your advantage: go slim, fire flame breath and jump on the next platform available. Mario can be used as a last resort as he can get high quick.
tamacrazy_101: The Wii version is the ONLY version called 'Super Paper Mario'. The other versions have different names.
People who are stuck on the three Chain Chomps, I did it without losing 1 hp!!!!
Use Piccolo to put the beast to sleep, then use Bowser's ordinary attack (not the flame breath it doesn't affect chomps.) Use Piccolo followed by Bowser every turn and that guy won't attack and you'll inflict maximum damage. If you don't have Piccolo, you're doomed.
Coco Boy: Count Bleck's castle? That's easy! Flip to 3D whenever possible to evade enemies and use loads of attack items. Then heal yourself using high-heal items like super/ultra shroom shakes and whacka bumps.