Before I say anything else about Little Big Planet I must address the sack in the room: sackboy is just that -- a sack. There is no way that he should be able to stand, or jump, or grapple, or self-destruct at will.
Either he is possessed by a demon (which is supported by the fact that all the non-sack NPCs speak in tongues), or he is the love child between Nightmare Before Christmas’ Oogie Boogie and a baby doll. I don’t want to think about either of those possibilities.
That’s just screwed up!
But wait....we're talking about physics. Right. Ahem.
I guess LBP is a physics platformer or something too, but let's be honest -- the real impressive defiance of physics in LBP is sackboy’s unnatural ability to exist at all.