So so far I'm fully done with Chapter 1 and 2 (Both Light and Dark worlds, A+ in all levels and the minus one levels). Is it possible to 100% the game with just Meat Boy? or some levels/picksup are only possible with other characters?
"One must keep his friends close Raziel, and his enemies, even closer.." -- Legacy Of Kain: Soul Reaver
You can beat all levels with Meat Boy, but I can think of one warp zone that is not reachable with him, and perhaps a bandage or two, not sure. And, of course, a lot of bandages or warp zones are easier to access with different characters.
In any case, all levels are beatable with him for sure.
"What kind of moron gets hit by a bus inside a shopping mall?" -Maria Torres, Trauma Team