The moment I saw all the Pokeballs flying, I got really hopeful for Greninja in some form or another, and then was kind of "ehh" when I saw Charizard, thinking that was the new announcement, but I was still happy to see him. Once the figure in the shadows was shown, though, I thought it was going to be like the Rosalina trailer where different game series were being crossed over, so I thought it was some ninja character from a game I hadn't played. When it started charging the shuriken, because of the lower quality, I thought it was some sort of ice blast (so... an ice ninja...?). The moment he went upright and I saw those horns, though, I honestly went ballistic. I'm usually a fairly composed person, but for about five minutes or so, I was overwhelmed by hype. Honestly, I thought Greninja had a chance as a Pokemon in a new Kalos-based Pokemon Trainer's roster, but a small part of me still hoped it could be its own character... and then it was.
Pretty sure Greninja may finally have managed to usurp Politoed's position as my favorite Pokemon at this point as well (you can probably see I have a thing for frogs XD). It definitely made up for the Oli nerf for me personally, and it's definitely been the most hype Smash 4 announcement for me thus far.