Fansite ArkhamCity.co.uk have spotted the first bit of artwork for Robin in Batman: Arkham City. For now, Robin is only available as a Best Buy pre-order bonus in the US. Hopefully we'll see him make his way over the pond at some point, or become available to all as DLC after launch. He'll be playable in all of Arkham City's challenge maps, and will get two unique ones of his own, called Black Mask Hideout and Freight Train Escape. Robin will fight with his own set of gadgets and will have a different moveset to Batman and Catwoman.
