Attachment
Saltonstall was a politician featured heavily in the game's 2010 gameplay demo but was cut during development. Despite this, he is referenced twice in the final game. First during the game's opening chapter where an NPC can be heard talking about him, and second in the chapter "Emporia" where a sign can be seen covered in scalps of prominent figures, including Saltonstall.
Contributed by Boyobmas
During the game's opening, the man who attempts to baptize Booker echos the phrase: "Is it someone new?" This is the same line spoken by the first splicer encountered in the original Bioshock.
Contributed by Boyobmas
Attachment
Bioshock's series creator, Ken Levine, has stated that he hates seeing pornographic fan art of Elizabeth. In a Reddit AMA, he said that it's like coming across porn of your own daughter, and that he "die[s] a little inside with every page view."
Contributed by KnowledgeBase
Attachment
In an early build of the game, the Barbershop Quartet in New Eden Square were called The "BEE" Sharps. In the final version, the band's name was replaced with "Albert Fink Presents." It's likely that the original name was a reference to The Simpsons, in which Homer was in a band called The Be Sharps.
Contributed by Pogue-Mahone
Located in the audio data of Burial at Sea Ep. 2, there is a file called "sfx_evt_inf_alley_loop_01". While it sounds like nothing more than creepy ambient music, if reversed and sped up 150%, it's actually an altered clip of Spoiler:Sally being burned at the end of the first episode.
Contributed by Some-creep
Some distant building models display an older Comstock graphic which does not reflect his final design. This suggests that these buildings come from earlier builds of the game, perhaps as far back as from 2010.
Contributed by Psychospacecow
Elizabeth was originally going to be mute, because Irrational Games wasn't confident in their ability to create a talking companion character, and were worried that repetitive chatter or quips would annoy the player. However, they felt that having to focus the camera on her for her to communicate visually interrupted the player's experience too much, and was also annoying. They were faced with the decision to either cut her completely, or commit to making her a speaking character, and the decision was very controversial around the studio at the time.
Contributed by DYKGal3rby
The ambient rumbling noise that can be heard in some parts of the game is actually music that has been pitch shifted downwards. Audio director Pat Balthrop was surprised that people discovered this by playing recordings of the game at high speed.
Contributed by frankfrost2
There is an unused vendor that was going to be used as a tailor machine. All of them are destroyed in game, although a single piece of equipment can be found within each of them. However, they have cut subtitles that seem to hint they were once going to be usable in the game.
Contributed by frankfrost2
At the end of the game, Spoiler:while exploring the various lighthouses with Elizabeth, an unused snowy hill, observatory and bridge can be found far off in the distance, hidden under the game's map. The door to the observatory is functional, but only leads to an infinite void.
Contributed by frankfrost2
One of the available Voxaphone recordings in the game is of Spoiler:Fink talking about seeing a blueprint of a merger between machine and man. This suggests that Fink had seen a Big Daddy blueprint through a tear.
Contributed by ghoststriker19
Attachment
The Old Man Winter Plasmid used in the "Burial At Sea" DLC was created by Joe Trinder. He posted the design on the game's official forums. Trinder's design was immediately praised by other fans, quickly gaining attention on Reddit and even earning the approval of BioShock creator Ken Levine. Within a day, Irrational contacted Trinder and asked for permission to publish the poster on their Facebook page. A month later, the team bought the design from Trinder, and told him they planned to use it in the game. His initial version was for a Vigor, but it was changed into a plasmid to fit with the game's DLC.
Contributed by Funland47
Spoiler:While in Rapture, Booker uses the Bathyspheres for transport. According to an Audio Log in Bioshock, the Bathyspheres were locked to Andrew Ryan's genetic code, and because Jack, the protagonist from Bioshock, had similar DNA to Ryan, he was able to use them. This may imply that both Booker and Elizabeth are in some way related to Andrew Ryan.
Contributed by GuiltyKarma
Attachment
When in front of the ticket salesman for the First Lady Airship, if you do nothing or demand the tickets, the salesman will stab you in the right hand, making Booker wear a bandage around that hand for the rest of the game. This is considered canon as this is how Booker is seen in all of his promotional art and even the front cover.
Contributed by gamemaster1991
Attachment
In the Warden's Office of Comstock House is a record player, with a record on it which reads "Rapture Records". This is a reference to the city of Rapture from the previous Bioshock games.
Contributed by Boyobmas
Attachment
Spoiler:Right after Songbird dies in Rapture, if you look out the window you can see a little sister crying over a dead Big Daddy.
Contributed by Boyobmas
Attachment
The propaganda poster featuring a little boy playing with toy soldiers and a little girl sitting on her father's lap asking him "Daddy, what did you do during the Siege of Columbia?" is based on a British World War I recruitment poster with the same illustration, but reads "Daddy, what did YOU do in the Great War?".
Contributed by KnowledgeBase
Attachment
After a competition held by Irrational Games for fans to submit their names to be used as part of an in-game advertisement, the lead artists had picked entrant "Payton Lane Easter". The advertisement created which incorporated the name was "Payton Lane Easter & Sons Premium Automated Stallions".
Contributed by KnowledgeBase
Attachment
In the Graveyard Shift Bar in Shanty town, if you head down to the cellar a guitar can be found. Elizabeth will state "I wish I could play" and if the player interacts with the guitar, Booker will start to play the guitar, and Elizabeth will sing along.
Contributed by SiiGMA Viperz
Attachment
The letter Spoiler:old Elizabeth gives to young Elizabeth says:

"I am a code. I should probably be changed over for something much more official in the future. But I'll do as a stand-in for now I suppose."

The developers likely forgot to change it.
The cipher used for the letter can be seen early in the game in one of Elizabeth's many rooms.
Contributed by JacobARF
The raffle at the beginning of the game may be a reference to the short story "The Lottery" by Shirley Jackson. Both lotteries are a big deal at the populated areas, and both end up with a stoning. It can also be said that in the story, the "winner" is selected by drawing from a hat, similar to the raffle in the game.
Father Comstock's name may be based off the Comstock Laws, a group of laws prohibiting the sending of any obscene materials, contraceptive devices, or information through the U.S. Postal Service. The laws were named after postal inspector Anthony Comstock, who was considered by many to have stepped far outside the bounds of his legal power.
Contributed by CopperRose
Attachment
In the cemetery containing Lady Comstock's mausoleum, explore the gravestones to the left of the entrance to her body. One of the graves, the only grave with legible hand-writing, says "SNIGHT" in bold letters. This is the personal signature of Mike Snight, one of the game's environment designers.
Contributed by DidYouKnowGaming
The whispers you hear when using the Possession Vigor is dialogue from Shakespeare's Romeo and Juliet being played in reverse.

A longer version with some extra lines can be found by extracting the audio from the PC version of Bioshock Infinite's game files. Part of this is used when you get the Vigor. The rest can be heard being whispered to victims of Possession during combat.
Contributed by DidYouKnowGaming
Attachment
After rescuing Elizabeth from Monument Tower and waking up on the beach, it was originally intended for there to be a scene where Booker spoke to a couple instead of Elizabeth. This was changed to have Elizabeth save you from drowning and asking Booker if she could go listen to music, as it would show that she cared about Booker. The couple are still on the beach in the final game.
Contributed by KnowledgeBase
Attachment
The map on display just before the Hall of Heroes is a possible reference to the map at the entrance of Disneyland. Both have similar banner designs and have a 'Main Street' at the center.
Contributed by DidYouKnowGaming
If you try to kill the Lutece twins at the Blue Ribbon, they will mock your attempts at trying to harm them (they are invulnerable).
Contributed by DidYouKnowGaming
Attachment
After Booker first sees the Monument Island statue and receives the telegram from Lutece, if you approach the telescope to the left and look through it, you can see the twins at the bottom left of the screen. Robert will be juggling as Rosalind watches. Exit the telescope and they are nowhere to be found.
Contributed by DidYouKnowGaming
When Elizabeth enters the Duke and Dimwit game room in Battleship Bay, she talks about the latest version of the game "Flawless Flintlock" being "delayed three times". This is a self-referential nod to the game's development cycle, as it was delayed three times.
Contributed by DidYouKnowGaming
Attachment
The Wrench from Bioshock can be found just after acquiring the Murder of Crows Vigor, and can also be seen on the First Lady Airship.
Contributed by DidYouKnowGaming
Inputting the "Konami Code" at the title screen (before beating the game) will unlock 1999 Mode.

On PC: Up, Up, Down, Down, Left, Right, Left, Right, Cancel key, Confirm key

On Xbox 360: Up, Up, Down, Down, Left, Right, Left, Right, B, A

On PlayStation 3: Up, Up, Down, Down, Left, Right, Left, Right, Circle, X
Contributed by DidYouKnowGaming
During seemingly music-less stretches of the game, an extremely slowed-down song is played in the background. When sped up, what seem to be voices can be heard in the song.
Contributed by DidYouKnowGaming
Throughout the game renditions of popular songs spanning the late 20th century can be heard. For example, when Elizabeth opens the tear to Paris, you can hear Tears for Fear's "Everybody Wants to Rule the World" (1985) being played. The quartet at the fair are singing the Beach Boy's "God only Knows" (1966), and the crowd at the raffle is singing Huddie Ledbetter's "Goodnight, Irene" (1933). Spoiler:This is part of a subplot, in which a rich music producer has heard music from the future through tears, and has gone on to produce and sell it in the current day (the past), making money on future hit songs.
Contributed by Milkman
Attachment
During the scene where you first meet Elizabeth, she tears a hole in reality to Paris. There is a theatre there showing 'la revanche du jedi', which translates to 'The revenge of the jedi'. This was the original name of 'Star Wars Episode VI: Return of the Jedi'.
Contributed by DannyHope95
Attachment
The statue titled "Comstock fights the Serpent of Nations" outside the Audemus Patria Nostra Defendere, bears a striking resemblance to a political cartoon of the USA's 7th president, Andrew Jackson titled "General Jackson Slaying the many Headed Monster". This could be due to how controversial these two men are, and wanting to rebel over something quite large.
Booker Dewitt was originally voiced by Stephen Russel (Garrett from the Thief series) until the team finally hired Troy Baker to take on the role.
Contributed by Dazz