You go to sleep for one night and the whole Internet goes nuts. Anyway, I was willing to believe this leak due to the photographs, but after the videos I'm totally on board with the leak. Here's my (brief) thoughts on the characters:
Bowser Jr.: Great idea. I think that Mario should have a lot of characters anyway due to being a massive franchise in the gaming world, and I think the concept of the Koopalings being alts is a great way to please classic fans. The Clown Car looks to be a lot of fun from the video and I'm looking forward to seeing more of it in action.
Dr. Mario: I actually like Dr. Mario due to being a fan of the DM games and for the fact that my brother made DM a huge in joke among my family and friends. He'd always kill people with lines like "We don't accept your insurance" and "You forgot to take your medicine." I also think it would be cool to have him back as he would have Mario's old DownB and he would have a different final smash.
Shulk: GREAT CHOICE! With Xenoblade being the huge hit that it is and a sequel on the way, it just made sense for Shulk to be in this. I'm a little surprised that he fights without the Monado at times, but I think he'd be a lot of fun to play as.
Duck Hunt: Now this is a WTF character. Duck Hunt was one of my favorite games as a kid, so I'll totally be playing as these guys. I'm excited to see what their moveset and final smash are.
Dark Pit: This is the only one I'm iffy on. I thought Uprising was great and I would love to see more of the Kid Icarus series in the future, but I think a clone of Pit is pushing it. If he has different moves then I'm for it. I could see Kid Icarus being the Star Fox of this game if anyone knows what I'm talking about.
The Cuts: I'm sad to see Wolf and Snake go, as I'm a huge fan of both series and felt they were great characters. I'm also disappointed that Lucas is gone as I felt that Mother deserved having two characters and I was looking forward to how his moveset would be changed from Ness. Ice Climbers I'm indifferent to. I'll miss them, but I'll get along without them. Ivysaur and Squirtle I'm also indifferent to as I played as the Pokémon Trainer, but having Charizard on his own and Greninja makes up for that in my opinion.
The remaining 3-5: Dixie I supported from the beginning and I would actually prefer her over K. Rool, as I've always liked heroes before villains. I just thought that she wouldn't have a chance due to being seen as too similar to Diddy, but since she was planned for Brawl, I could see Sakurai going back to her and making her work here. Ridley I've wanted since Brawl and I think him being revealed as a boss would be a huge rip-off after all the teasing. Mewtwo I've also wanted back since Brawl showed that he was cut and I totally expect him. Impa I'm indifferent to, although I do think she would be a good choice what with her increase in roles in the Zelda series. I actually wanted Sheik to get cut and have impa replaced her. Mach Rider I think would be an awesome choice just for that retro representation and no one would see it coming (Although I think he was planned to be the original Captain Falcon Clone back in Melee, so maybe some hardcore fans would expect it.) Chorus Men I'm also indifferent to. I actually bought Rhythm Heaven Fever because of the Gematsu leak, and I thought it was an awesome game, but I would rather have a stage or someone else from that franchise.
Anyway, this leak is really exciting and I'm definitely getting more hyped to play the games! I'm looking forward to seeing what gets officially revealed and also what gets leaked in coming weeks.