"Hello, I know this will probably be buried under a lot of speculation, however I am leaving my career after a few years and I've decided to speak about what I know about this game.
A little backstory, I worked for a little animation company called "Spooky graphic". We worked a little bit on the animated trailers for Smash Wii U, and we were asked to help with this new game too. I personally specialise in effects, including for example the dust you see when the characters land in the Duck Hunt trailer. I also worked on the lighting for Mega Man's trailer. Including a Spark Shock move featuring Pikachu that got unfortunately cut.
Because I have only worked on the trailers, I was only ever given what I needed to. I don't have any attack information, and I can't say that there aren't other character trailers being worked on. We were supplied with screenshots and animation references however, to make sure the animation is accurate.
So far, the company has been hired to work on two trailers. The first one appears to be a King K. Rool trailer. The trailer is a comedic take on a heist movie, with Wario, Wolf and Ridley planning to steal a large pile of bananas from Donkey Kong. I mainly worked on the physics for the scroll map, however I did do dust trails for the end of the trailer where King K. Rool is running away with the stash in a wooden cart. I know that at one point he uses a giant cannon (smoke effects) so this is likely one of his specials.
The second and last trailer I worked on is for a character that from what I can tell isn't highly requested, but should cause a lot of excitement. It's a trailer for Gengar. The main theme of the trailer is the haunted house genre, starring Ness, Lucas and Toon Link (in pajamas). It appears to be a sleepover scene, with the kids telling scary stories. The house starts doing strange things, including moving chairs, animating paintings and strange noises. All of these effects use an aura, so I worked quite heavily on this animation. Eventually, both Toon Link and Ness are swallowed by a black void, leaving only Lucas. The wall then grows a smiling face, and Gengar emerges from it.
I wish I could give you moveset information, however that doesn't appear to be possible for Gengar. His character model is translucent however, and that would likely be a feature in his actual character. Other than that, all I can say is that he's in the game.
The reason I can legally divulge this information is actually the reason I am leaving the company. I was seriously ill a while ago, and was out of work for a few months. Those were the months that Nintendo demanded non-disclosure agreements, and I was overlooked. By the time I had left, nobody had asked me to sign anything, so as far as I know I'm under no obligation to keep this secret. The illness has returned, and I am unable to work because of it."
