Charizard time.
It got a new Forward Air.

Its old forward air was was a small flame burst. It was okay for keeping opponents away from the stage, but the range was really short and it wasn't that powerful. It was also a bit redundant since Rock Smash (Side B) was better and did the same thing basically. Whether this is a good change or not has yet to be seen, but I feel this can have a lot more use than its old forward air.
Flare Blitz?

So this looks like Charizard's old Up Special except it is going side ways and you couldn't do that in Brawl. And it didn't have as much fire showing as it does here. It looks to be really powerful.
Looking at it frame by frame, Charizard's knock back could have been caused by Wii Fit Trainer's Down Smash, but it doesn't seem like Wii Fit Trainer managed to use it.
So I'm going to assume it is actually caused by whatever move Charizard is using. It reminds me of the move in the Pokémon games called Flare Blitz which is a powerful physical attack where the user just charges at the opponent in flames, but because it is powerful, the user is hurt in recoil which is what seems to happen to Charizard here. It could be a new Up Special, Side Special, or Down Special. We'll find out what it is soon enough.
EDIT: And we did, it is its
Side Special.
Mega Charizard X

So yea, this is Charizard's Final Smash. No surprise this is here since Game Freak/The Pokémon Company have been promoting this A LOT throughout various ways. Though there is some confusion regarding if mega evolutions are final smashes. I think they are.
But people refer to the
lack of a dark background when Mega Lucario is shown, yet there is a dark background when Mega Charizard X is shown. I think there is a simple explanation to this.
I think Mega Lucario is going to be similar to Giga Bowser or Wario-Man where you can control the character in the different form doing all the regular moves you would in its normal forms, but with some different properties.
And I think Mega Charizard X is going to be similar to Yoshi's Super Dragon or Diddy's Rocketbarrel Barrage. I'm guessing it will spit out some blue flames or something.