Obviously, these are the newcomers to the series. Any character not previously playable through official means goes here. These will usually get explanation. They also aren't grouped by series, either.
King K.Rool: The main villain of the Donkey Kong Country franchise, and undoubtedly the most famous of DK's foes, King K.Rool absolutely deserves to be in Super Smash Bros., especially over other canidates like Cranky or (god forbid) Brash. King K.Rool could be an interesting character, especially since he has so many different forms to play with, like Baron K.Roolenstein, Kaptain K.Rool and King Krusha K.Rool. A heavyweight fighter with decently quick speed would be a fresh way for this series to go, and K.Rool would be perfect for it.
Tyrantrum: Revived from a Jaw Fossil, Tyrantrum evolves in the day from a level 39 Tyrunt. Arguably one of the most popular of the Fossil Pokémon, Tyrantrum would be in a weight class of it's own, making him the heaviest fighter in the game. Tyrantrum would also be pretty big as a fighter, as well, standing over a head taller than Bowser and hitting like a 300-mph truck on legs. He'd be slow, but powerful and with a good amount of superarmor. The hefty weight reduces his air game to flailing around to try and get hits in during the small span it's in the air, but on the ground Tyrantrum would be difficult to bowl over. As a representative of the Fossil Pokémon, Tyrantrum would be a good choice to go with.
Ridley: Giger-esque design? Check. Important to origin series? Check. One of the most desired characters in the series'
history? Check. Ridley would be the
ultimate newcomer reveal to hype up a new Smash game; he's got a lot of backing, is important to Metroid canon and is ultimately a freaking
Xenomorph-esque dragon. How
cool would that be to play as? Now obviously, there'd be complaints of downsizing, but as the newcomer above has proven, I really don't care about making them decently scaled, so long as it looks good and isn't broken. And a Ridley about the same size as Tyrantrum would be about as good as anything; it'd keep him as a fighter while keeping him from being
too alien. He'd be something like the opposite of Tyrantrum; great aerial game and good ground game.
Other Newcomers (formatted in a list): Extra Mii Fighter class (maybe a Marksman?), new third-party character, some inevitable clones, Waluigi, a number of potential others through DLC...too many to list.