While Playing the game make sure you leave Penguin as your last boss (Just make sure you don't go too the Lighthouse area until you defeated Joker and Black Mask). After entering the Arkham wing catwoman will tell you too rescue all penguins hostages and you will be given the map locations. Each hostage has one guard holding them hostage (Silent Takedowns don't work on these guards) you must defeat these guards by using your Bat-Claw then press A on the Hostages.