* BTeamSequel: 2k Marin took on the task of creating a direct sequel to ''VideoGame/{{Bioshock}}'' to free up Irrational to work on ''VideoGame/BioshockInfinite'', which, as it involved an entirely new setting, took much longer.
* {{Defictionalization}}: [=NECA=] has replicas of the EVE Hypo and Big Daddy dolls, just in case your normal Little Sister wasn't creepy enough. They also have one for the "bunny" and "wielder" Splicer masks.
* NamesTheSame: This game isn't [[{{Series/DoctorWho}} the only work]] to have character named [[Recap/DoctorWhoTVMTheTVMovie Dr. Grace Holloway]].
* ThrowItIn: "[[ViralMarketing Something In The Sea]]" wasn't going to have an effect on the main game, but fans loved it so much that protagonist Mark Meltzer was given a minor role.
* WhatCouldHaveBeen: A DummiedOut idea for the plot would have involved [[DirtyCommunists Soviet soldiers]] invading Rapture. Part of the AI coding intended for the Russians eventually ended up being used by the splicers instead.
** A removed message from Eleanor revealed that Delta is her biological father (Sophia picked his DNA randomly from a bunch of archived DNA).
** Dionysus Park was originally conceived as being as a perfectly intact area that wasn't leaking and falling apart like the rest of Rapture. The player was originally supposed to get there by way of an underwater section through a completely flooded [[NostalgiaLevel Fort Frolic]].
** The Rumbler is an updated version of a cut Big Daddy from the previous game (which even made it onto some screenshots) code named "Slow Pro FUM" ("slow-moving, projectile-shooting, f'ed-up-melee"). The SPF had a single cannon which he had to kneel down in order to use and a huge hook for heavy damaging melee attacks in case the player got close. The SPF ended up being cut late in development, much to the chagrin of the designers. Eventually it was reworked into the Rumbler, with the hook replaced with the mini turrets (since they believed the Bouncer had the heavy melee department covered).
** Originally there was only going to be a single Big Sister who would be the real BigBad of the game: one of Jack's rescued Little Sisters who couldn't adjust to life on the surface and would return to Rapture and recreate her childhood by kidnapping children to make into new Little Sisters. In another version, Sofia Lamb would still be the BigBad, but there would still be a single Big Sister as TheDragon, which would be revealed to be Eleanor (hence why in Audio Diaries Sofia still refers to Big Sister in the singular). Thus you would fight the Big Sister in a series of [[HopelessBossFight Hopeless Boss Fights]] where you had to survive and damage her enough for her to retreat. Eventually the developers scrapped this since they felt knowing that the Big Sister would always escape would undermine the excitement of the battles as well as feeling that "the Big Sister being YOUR Little Sister" was a weak twist. [[spoiler: In a way they partially kept the twist, with ONE of the Big Sisters being the protagonist's Little Sister-only she was Delta's Little Sister, not Jack's.]]