Easter Egg #6: Ra's al Ghul Never Dies: After Ra's al Ghul kills himself during his fall from Wonder Tower, he is impaled on the Arkham City sign.

Killer Croc bursts out of the wall, threatens Batman, and returns to the murk. Once there, throw a Remote Control Batarang through a small hole in the bars and hit the button on the other side. Instead of following the current objective, go to the easternmost part of the Subway Maintenance Entrance.

Easter Egg #5: Killer Croc: After defeating Ra's Al Ghul for the first time, you can find Killer Croc.

By using a Vigenere Cipher with the keyword ' Scarecrow' the message will read 'Fear will tear Gotham to shreds.'

This is the most difficult to decode, and requires a keyword to translate. It can be decoded in a Caesarian Shift, where the alphabet is shifter down, in this case Z=1, Y=2, X=3, etc. It can be decoded via simple Caesarian Cipher, in which A=1, B=2, C=3, etc. These numbers can be deciphered with three different methods: The first can be heard on the broadcast 700.00 x, 500.00 y and reads '9 23 9 12 12 18 5 20 21 18 14 2 1 20 13 1 14'.

Easter Egg #4: Secret Coded Messages: After beating the game, using the Cryptographic Sequencer will reveal three separate messages on three various signals and at the end a chime.

She had previously done this in Batman Beyond: Return of the Joker.

Easter Egg #3: Harley Quinn Singing 'Hush Little Baby': After beating the game on New Game Plus Mode, you can hear Harley Quinn singing a distorted version of the lullaby Hush Little Baby.

In it, the Clown Prince disturbingly sings Only You (And you alone) by The Platters.

Easter Egg #2: Joker Singing 'Only You': After beating the game on any difficulty, a missed call from Joker plays.

Here, once again, is a test that states 'May provide false positive.' The test reads positive, hinting that Harley may in fact be pregnant with Joker's child, but in the DLC Harley Quinn's Revenge, there are more pregnancy tests that read negative, excluding one positive sitting next to a box a label on its side reading, 'May provide a false positive.' There is also a crib in the office that has the Scarface puppet in it, dressed as the Joker.

Easter Egg #1: Harley Quinn Pregnant: In the Manager's Office of Joker's Steel Mill is a pregnancy test right beside Harley Quinn's outfit from Arkham Asylum.

WARNING: THE FOLLOWING ARTICLE CONTAINS SPOILERS! READ AT YOUR OWN RISK!

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