MultiVersus, which will be a free-to-play game, is a cooperative, four-player platform fighter, a la Super Smash Bros. Based on the trailer, the initial roster appears to include, among others:
Jake the Dog and Finn the Human (AdventureTime)
Harley Quinn, Wonder Woman, Batman, and Superman (DC Comics)
Tom and Jerry (Tom and Jerry)
Arya Stark (Game of Thrones)
Shaggy (Scooby-Doo)