Easter Eggs

This is a list of Easter Eggs in the Batman: Arkham Series.

Batman: Arkham City Lockdown

 * #1: Batman vs. Kano: If you start the EMP challenge in the Sionis Steel Mill, you can fight Kano from Mortal Kombat as the last enemy during the challenge's sections.
 * #2:: In the Game Over for the boss fight with Deathstroke, he will be heard talking to his client over a radio. The client is actually Hugo Strange, who uses one of his Game Over lines from Arkham City.
 * #3: Batman and Robin: Poison Ivy brainwashing Tim Drake is similar to her attempted seduction of Dick Grayson in Batman and Robin.

Batman: Arkham Origins Blackgate

 * #1: Task Force X/Suicide Squad: Catwoman states she was hired anonymously by an unknown party. This same party monitors the events at Blackgate Prison, especially Batman's fights with Deadshot and Bronze Tiger. Richard Flag reveals that he and a group of soldiers captured Bane after he broke out during the riots, which Batman says were incited specifically to free him. Flag tells Amanda Waller about this, but she has already had him erase Catwoman's criminal records and released Deadshot and Bronze Tiger into her custody.
 * #2: Secret Scenes: There is a different secret ending for each villain you defeat last.
 * #2a: The Joker: Joker is on the floor laughing as two guards walk up to him. He then uses spikes hidden in his teeth to kill the guards and takes one of their uniforms. The disguised Joker fools two more guards, and when they move out of earshot he pulls up the helmet visor and laughs.
 * #2b: Black Mask: A guard comments on how Black Mask screwed up piping and temperature controls in Blackgate by attempting to overload the generators. The unconscious Black Mask then suddenly awakes and grabs the guard watching him hostage, demanding to see Joker so he can get his revenge. When demanded to release him the former mob boss pushes his hostage away and opens fire, causing the guards to return the favor. The guard who was being held hostage tries to warn the others about hitting the weakened pipes, but they ignite in a pressurized burst of flame as Black Mask screams in agony. When the smoke and steam clears, Black Mask is gone and one guard says Joker should watch out for his former victim.
 * #2c: Penguin: A corrupt guard helps Penguin get loose from where Batman left him, only to be beaten for mouthing off. When Penguin requests his belongings, the guard points to his umbrella and the crime lord notes how Batman still interfered with his plans, even behind bars. When the guard says there are 132 gang members total, Penguin remarks that there is one less as he stabs the guard, commenting on his insubordination.

Batman: Assault on Arkham

 * #1::

Batman: Arkham VR

 * #1: Wake Up, Bruce!: There are hints that Bruce Wayne/Batman is actually dreaming and subconsciously trying to break out of a Joker Infection-triggered nightmare. Using the Batcave's surveillance equipment to tune into the 254Mhz frequency, a transmission sends out these numbers: 23, 1, 11, -1, 4, 20, 15, -8, 19, 9, 12, -10, 10, 12; using the Shift (or Caesar) cipher they translate to "WAKE UP BRUCE". Another clue is the lullaby "Rock-a-bye Baby", which can be found in its original form Lillibullero on a music sheet for the piano in Wayne Manor. Different versions can be heard from Martha Wayne's music box in the manor lounge, on the Batcave's radio after Penguin's interview, and in the background of a coroner's third recording in the morgue of Gotham General Hospital. You can hear the sound of an alarm clock at the beginning, on a radio broadcast in the Batcave that mentions oneirology, and when going down the elevator in Arkham Asylum. After taking down his thugs and confronting him by dangling him off a ledge, Penguin yells at someone to wake up.
 * #2: 425: This magic number is a reference to Joker's comic debut on April 25, 1940. The combination to the safe in the hospital's morgue is 425, the final entry of the coroner's recordings has Joker giving an autopsy report at 04:25 pm, and two of the items kept as evidence in the morgue are labeled as Evidence 425-176 and Evidence 761-425 respectively. The phone in the Batcave has the frequency 0.425, and the police dispatcher on the Batcave's radio scanner has the frequency 425Mhz, also mentioning the number a few times. The code S425 appears on dumpsters when investigating Nightwing's murder. Inside a locker in Arkham Asylum there is a mug with the Arkham logo marked 425 on the bottom. Joker's cell in the nightmare has the number 425. The number and plot were teased in the newest Wayne Manor Challenge Map; if you interact with the grand piano the chime of Arkham will play and a hidden wall with information about the dream will be revealed.
 * #3: Catwoman Heists: Scattered around Wayne Manor are postcards signed by Selina Kyle, better known as Catwoman from all over the world. Each postcard corresponds to newspaper clippings of jewelry thefts pinned to the globe in the lounge area.
 * #4: The LexCorp Takeover: In the Wayne Manor Main Hall, there is a large model of Gotham City with toppled buildings. Putting them back in place uncovers a statistical document of Wayne Enterprises against LexCorp and how many holdings the latter has acquired in Gotham.
 * #5: The Pianist: You can actually play the piano with both fingers.
 * #6: Secrets of the Batcave:
 * #7: Arkham Knight: In Arkham Asylum, you can faintly hear Jason Todd's screaming and Joker's laughter overlapping with each other in the background.
 * #8: Batphone and Messages:
 * #9: Killer Croc: In a sewer pipe, you can briefly spot Killer Croc stalking you.
 * #10: Mad Hatter: On a fire escape balcony in the alleyway where Nightwing's body is, you can turn around and see through an apartment room window a green top hat, a model of an Alice in Wonderland scene and a poster representing Batman's encounter with Mad Hatter in Arkham City. This is really his room, and zooming in will unlock the trophy "Through the Looking Glass".
 * #11: Batman's Past Failures: On the rack of a body container in the morgue there is a keycard which opens up a freezer, and inside you can find the Titan Disease-infected blood Joker had Strange deliver to various hospitals, the gun he used to paralyze Barbara Gordon, the crowbar he used to beat up Jason, and one of Nightwing's Escrima Sticks which was recovered from the scene of his murder. Scanning them unlocks the "Fallen Son" trophy.
 * #12: Joker's Bio:
 * #13: Arkham Asylum: In Arkham before reaching Joker's cell, a keycard in the second hall opens a storage locker for Aaron Cash. It contains a photo of his family, his prosthetic hook, and a map marked with sightings of Killer Croc, who he lost his real hand to. At the check-in desk you can find a poster for Metropolis, as well as a list with the names of Victor Zsasz, Arnold Wesker (aka the Ventriloquist), and Joe Chill. The Ventriloquist's dummy Scarface can be found in cell 423, and each time you turn away he takes a different position.