Characters in Earth One

Batman

Also in Batman: The Dark Knight Returns, Batman, Batman, son of the demon, The Caped Crusader, Vol. 2

Riddler

Killer Croc

Alfred Pennyworth

Also in Batman (1940-2011) #1: Special, Batman: Bruce Wayne, Fugitive, Batman, Volume 1: The Court of Owls

James Gordon

Also in Batman: The Dark Knight Returns, Batman, Batman (1940-2011) #1: Special, Batman, son of the demon, Batman, Volume 1: The Court of Owls, Batman: Zero Hour