The confirmed characters are: Kratos (God of War series), PaRappa (PaRappa The Rapper), Sly Cooper (Sly Cooper series), Colonel Radec (Killzone series), Sweet Tooth (Twisted Metal series), and Fat Princess (Fat Princess series). There will also be confirmed locales such as the underworld setting for God of War's Hades, Ratchet and Clank's cityscape Metropolis, and so on. PlayStation Blog has also detailed that the game will have single and multiplayer game modes, as well as online play with a "robust" tournament option. I would also love to see Crash Bandicoot, Solid Snake, and Nathan Drake in the game, hopefully they will be confirmed. More details will come soon.
God Bless and Play Hard Gamers!