Bunch of things I noticed (other people may have too, that's fine, but just putting them in the thread):
*In the clip on the Bridge of Eldin, the Smash Ball is floating in the air, moving diagonally down-left, kinda towards the hole in the middle. Fox does his side+B to the left, crossing the gap, and goes through the smash ball. It makes a breaking sound. The trailer cuts to what appears to be a split second later, and fox has turned into the tank. This would imply that a Smash Ball is like a Capsule, and when you 'open' it, your final smash activates.
*The clip of Lucas shows him doing what appears to be a B move that Ness does not have - increases Ness's chances of returning/being dissimilar to Lucas.
*The Ice Climbers are doin a little dance in a stage with the Northern Lights in the background. This implies it's either an Ice Climbers stage or an adventure mode level with a "cold" theme.
*There are two shots - one of Wario and Torchic, the other of Charizard - that take place in an underground level full of lava, with futuristic looking metal platforms. Either an Adventure level, or my guess is Magmoor Caverns? (Metroid Prime)
*Kyogre, Torchic, Snorlax confirmed
*When DK is blasting from barrel to barrel in Adventure Mode, he arrives at a glowing blue and red treasure chest - what's inside? Could this be the percentage we saw in the world map update?
Also in the other movie, Sonic jumps off a red spring from his games in Delfino Plaza - probably his up B.