Seems like there is a new trailer for Batman: Arkham City. In it the Batman and Joker team up to take down some goons. It tells us nothing, reveals nothing, but we get to see two minutes of comic characters kicking some ass. I'm not sure if we can count this as confirmation that the Joker will be in the new game or if this is just to show off some co-op mode outside of the standard game.
You can watch the trailer here.
via VG247