Now this is an interesting one! Mr. Sakurai tells us that Little Mac’s side smash is a straight right… but can also be an uppercut or a body blow. We’re used to “tilted smash attacks” – many characters can initialize these already. In the past, these have just pointed the same attack up or down a bit and changed damage/knockback properties. What we’re seeing with Little Mac’s tilted smashes are big changes to the animation and, safe to assume, the damage/knockback. Sakurai says that the body hook (the down tilted forward smash) is the most “devastating,” but doesn’t knock opponents away. My guess is this points to it doing the most damage and possibly adding something akin to a crumple effect, like Street Fighter IV’s Focus Attacks. You’ll be able to tell which one Mac is throwing, since the animations are very different, as are the visual effects on each strike.
Little Mac seems chock full of new mechanics to play around with, and that’s entirely a good thing. His speed is also a hopeful indicator of the overall game speed, for those of us who are hoping for something between Brawl and Melee gameplay wise.