It was recently revealed that Nightwing (AKA Dick Grayson, the original Robin) will be a playable character in Batman: Arkham City as well. Nightwing will be made available in the form of a DLC pack, which will be released on November 1st.
The Nightwing Bundle Pack will come with two new challenge maps: Wayne Manor and Main Hall. Like Catwoman and Robin, Nightwing will be playable in all challenge maps in the game, and will have his own moves and gadgets. The Bundle Pack will also include a Batman: The Animated Series skin for Nightwing.
Robin, originally announced as a pre-order bonus, will be available via a DLC pack, too. The Robin Bundle Pack will go on sale on November 22nd. Each DLC pack will cost 560 Microsoft Points or $6.99 / €6.99 / £5.49 on the PlayStation Network.