All costumes...
	Alternate ending...
	Big head mode...
	Cryptographic Sequencer Cipher...
	Easy "Story Teller" achievemen...
	Harley Quinn pregnancy...
	Harley Quinn's Revenge: Achiev...
	Hidden messages...
	Killer Croc reference...
	Lost reference...
	New Game Plus mode...
	Scarecrow Room...
	Taunting...
	Various Achievements...

At the main menu, press Left(2), Down(2), Left(2), Right, Up(2), Down to unlock an option to select any of the bonus costumes. If you entered the code correctly, you will hear a sound when you continue your game.

The alternate ending requires the bonus "Catwoman" downloadable content. In Catwoman's third mission, when you have the option to go left or right with the "loot", go right to view the alternate ending. You will still be able to go backwards and not ruin anything in the main campaign.

Hold LB + RB and rotate the Right Analog-stick clockwise ten times. Repeat the code to disable its effect.

If you open up your Cryptographic Sequencer, you can find three broadcasts from a slightly fuzzy and robotic voice saying seemingly random numbers. These numbers are actually a cipher, numeric representations of the alphabet. Two of the broadcasts are garbage, but the third one says: "9 23 9 12 12 18 5 20 21 18 14 2 1 20 13 1 14" which translates to " I WILL RETURN BATMAN".

Play offline (not logged into Xbox Live or PlayStation Network as your system date is automatically set via the internet). Set the date of your console to one of the following dates: January 1st, Feburary 14th, March 17th, April 1st, May 8th, June 19th, July 4th, August 16th, September 5th, October 31st, November 24th, December 25th. Then, load a saved game file where the story progress is past rescuing Catwoman. Enter the courthouse and talk to Calendar Man in the basement. He will tell you a story about the current month's holiday and tell you to return for the next month. Save the game by leaving the building. Exit to the system settings, then manually change the date to the next holiday. Repeat the process until you have cycled through the entire calendar year. The calendar on the wall next to his cell will highlight the holiday dates for the current year and scribble out which months you have already spoken to Calendar Man about.

Go to the manager's office inside the Steel Mill. On the floor, next to the Harley Quinn costume, there is a positive pregnancy test.

Complete the following achievements to unlock Xbox Live Gamerscore points.

Achievement	How to unlock
A Few New Tricks (20 points)	Use 5 different Quickfire gadgets in one fight as Robin in Harley Quinn's Revenge.
Battering Ram (10 points)	Shield Bash 5 different thugs.
Bomb Squad (40 points)	Defuse all bombs in 3 minutes or less.
Breaking and Entering (20 points)	Find a way into the secret base.
Frequent Flyer (10 points)	Zip Kick 5 different thugs.
How's It Hanging? (20 points)	Clean up the Dry Docks.
Lost Property (20 points)	No crimefighter should be without this.
Party's Over (50 points)	Destroy all Harley Balloons.
Snap To It (20 points)	Snap Flash an unarmed thug, an armed thug, an environmental object and a Titan.
The Last Laugh (40 points)	The joke's on who?

Find the coordinates X700.00, Y490.00 on the Cryptographic Sequencer to intercept a radio frequency that contains the following repeating numbers: 9, 23, 9, 12, 12, 18, 5, 20, 21, 18, 14, 2, 1, 20, 13, 1, 14. The message is decoded as "I WILL RETURN BATMAN".

Find the coordinates X500.00, Y900.00 on the Cryptographic Sequencer to intercept a radio frequency that contains the following repeating numbers: 5, 15, 9, 7, 21, 18, 18, 14, 3, 5, 24, 15, 12, 7, 22, 3, 10, 5, 15, 9, 22, 3, 8, 25, 26, 15, 16, 25, 10, 15, 17, 25. The message is decoded as "YOU WILL PAY FOR WHAT YOU HAVE DONE TO ME".

The last radio transmission contains the numbers: 3, 20, 26, 18, 26, 16, 24, 1, 11, 4, 24, 9, 3, 8, 5, 2, 12, 18, 6, 16, 7, 11, 3, 10, 17, 5, 13, 4, 21, 8. The message is decoded as "FEAR WILL TEAR GOTHAM CITY TO SHREDS".

After you defeat Ra's al Ghul and are leaving the subway tunnels, instead of going the correct way, backtrack until you find a gate blocking your path. You should see a button on the far wall and a gap in the iron bars. Throw the Batarang through the gap to hit the button. There will be a cutscene with Killer Croc. Note: You cannot reach this area again after this point in the game.

Play the mission where you have to get the cure back from Joker. There is a part where a video plays featuring the Joker ranting about the ending to the show Lost.

Successfully complete the game under the Normal or Hard difficulty setting. This mode allows you to keep your previously earned gadgets and experience points. Also, there will not be any counter icons on thugs, thugs will be more difficult from the start, thugs will have different configurations, and Bosses will be tougher.

On a ship near the complete bridge going between the Industrial District and Amusement Mile, there is a tiny raised area on it. If you stop on this little platform and take out your Cryptographic Sequencer, you will start hacking something. This hack is very tough, but after you get it the trapdoor opens. When you go down you'll see several hundred bugs scurrying around and a dead henchman. If you zoom in on the henchman he will move a little bit. To the right of the henchman is a clipboard with Dr. J Crane's name on it, and an order for several thousand of those bugs.

Rotate the Right Analog-stick clockwise repeatedly to perform a taunt. Note: If you execute a taunt before performing a glide kick with Batman or Robin, the view will change to the enemy's perspective.

Complete the following achievements to unlock Xbox Live Gamerscore points.

Achievement	How to unlock
I'm Batman ( 10 points )	Become the Bat.
Acid Bath ( 10 points )	Save the damsel, but is she in distress?.
Savior ( 10 points )	Save the medical volunteers.
Chimney Sweep ( 10 points )	There is only one way in.
One Armed Bandit ( 10 points )	Hammer the point home.
Communication Breakdown ( 10 points )	Clear the airwaves.
Gladiator ( 10 points )	Last man standing.
Wrecking Ball ( 25 points )	Stop the unstoppable.
Lost And Found ( 10 points )	Uncover the secret of Arkham City.
Sand Storm ( 25 points )	We are legion.
Hide And Seek ( 25 points )	A deadly game of hide and seek.
Ghost Train ( 25 points )	Fight for survival.
Freefall ( 25 points )	Don't look down.
Exit Stage Right ( 50 points )	All the world is a stage.
Forensic Expert ( 10 points )	Collect enough evidence to locate the gun for hire.
Contract Terminated ( 25 points )	Stop the contract operative.
Serial Killer ( 25 points )	Track down the serial killer.
Mystery Stalker ( 15 points )	Reveal the mystery watcher.
Distress Flare ( 5 points )	Answer the call for help.
Broken Toys ( 25 points )	Destroy it all.
Ring Ring ( 5 points )	Answer a ringing phone.
Dial Z For Murder ( 25 points )	Stop the phone booth killer.
Stop the Clock ( 15 points )	Time is running out.
Bargaining Chip ( 15 points )	Reunite the separated couple.
AR Knight ( 25 points )	Complete all augmented reality training exercises.
Fully Loaded ( 10 points )	Collect all of Batman's gadgets and upgrades.
Aggravated Assault ( 10 points )	Stop all assaults in Arkham City.
IQ Test ( 10 points )	Solve the first riddle.
Conundrum ( 20 points )	Rescue the first hostage from Riddler.
Mastermind ( 20 points )	Rescue the second hostage from Riddler.
Puzzler ( 30 points )	Rescue the third hostage from Riddler.
Intellectual ( 30 points )	Rescue the fourth hostage from Riddler.
Brainteaser ( 40 points )	Rescue the fifth hostage from Riddler.
Genius ( 50 points )	Rescue all the hostages from Riddler.
Bronze Revenge ( 10 points )	Obtain 24 medals on the original Arkham City ranked maps ( as Batman).
Silver Revenge ( 20 points )	Obtain 48 medals on the original Arkham City ranked maps ( as Batman).
Gold Revenge ( 40 points )	Obtain all 72 medals on the original Arkham City ranked maps ( as Batman).
Campaign Bronze ( 10 points )	Obtain 24 medals on the original Arkham City ranked maps ( as Batman).
Campaign Silver ( 20 points )	Obtain 72 medals on the original Arkham City campaigns ( as Batman).
Campaign Gold ( 40 points )	Obtain all 108 medals on the original Arkham City campaigns ( as Batman).
Flawless Freeflow Fighter 2.0 ( 5 points )	Complete one combat challenge without taking damage ( any character).
Twice Nightly ( 75 points )	Complete New Game Plus.
Gotham Base Jumper ( 5 points )	Jump off the tallest building in Arkham City and glide for 1 minute without touching the ground.
Pay Your Respects ( 5 points )	A moment of remembrance.
Story Teller ( 10 points )	Have 12 murderous dates with Calendar Man.
Catch ( 5 points )	Find someone to play remote Batarang catch with.
50x Combo ( 5 points )	Complete a combo of 50 moves ( any play mode, any character).
Perfect Freeflow 2.0 ( 5 points )	Perform a perfect combo including all of Batman's combat moves ( any play mode).
Gadget Attack ( 5 points )	Use 5 different Quickfire gadgets in one fight ( any play mode).
Perfect Knight - Day 2 ( 75 points )	Main Story, Side Missions, Upgrades, Collectables, New Game Plus and Riddlers Revenge ( as Batman).