Every Character ever is returning.
Image mock-up attached.
--Newcomers: Ridley, Inkling, King K Rool, Ashley, Paper Mario, Karate Joe, Simon Belmont. Impa, Daisy, and Alph are clones. Yes, I know Alph has been "confirmed" as a costume. Its a lie, apparently.
--Returning Unconfirmed Stages: Rainbow Cruise, Delfino Plaza, Paper Mario, Big Battlefield
--New Stages: New Donk City, Diamond City, Gangplank Galleon, Airboarder, Melemele Island, Brain Age, Robotic Operating Buddy, Dracula's Castle, Biosphere, Temple of Mila. Yes, one of the stages you fight on top of a gigantic R.O.B. It's weird, I know.
--Stadium Mode: Multi-Man Smashes, Home Run Contest, Target Smahes - grouped by seres, some sort of bowling mini-game where you crash foes into bowling pins.
--Single Player Misc: Classic, Events, Master Orders, a story mode - not like SSE - more segregated - cool cutscenes tho.