History DevelopersForesight / DeusEx

** If you actively avoid Stephanie Maxwell (the scientist who begins talking to you within two seconds of beginning the level) and either run to another part of the roof or go into the building, Jock calls and relays everything that Stephanie would have said, up to and including a keycode that he had no way of knowing himself. Likewise, Stephanie's dialogue changes after this.
** Stephanie has additional dialogue if you go back up to the roof and talk to her after destroying the four sentry bots, despite there being no other reason to visit. This can also be accomplished if you manage to destroy all four bots from the roof (either with Spy Drones, Scramble Grenades or conventional arms).

* Invoked in-game with the "Time Traveler" achievement. You can choose to retrieve the neuroplasticity calibrator for Koller from Otar Botkeveli's casino ''before'' you're asked to. Doing so causes an entirely different cutscene . Koller is gobsmacked when Adam reveals he has the calibrator, but says that he's not ready to dive in just yet. He also tells Adam to contact Sarif, and says that he's going to do some research before installing it. It should be noted that doing this also makes the mission chain involving Otar's errands unavailable, making this sequence more of a curiosity for enterprising players. So if you're trying to get most of all achievements in one playthrough, it's best to make a save before deciding to do this.

* Later in the game, when the player accepts Chad's mission to find and rescue [[spoiler:Her Holiness, a.k.a. Nicolette Duclare, a.k.a. Chad's wife]] from the complex in Trier, you can choose to shoot and kill the character during the one instance you meet her (as opposed to Chad, who retains PlotArmor for the duration of the mission]]. Killing the character nets you a WhatTheHellHero moment from Chad, but ultimately keeps the plot on track.

** When Walton Simons arrives at UNATCO, and JC does not intrude on Walton Simons interrogating [[spoiler: and executing]] an NSF prisoner, as JC leaves for his next assignment, the Men In Black outside the UNATCO building will tell JC that he may board the helicopter in a calm tone of voice, as they appreciate JC for his understanding. Otherwise, if JC does intrude, the Men In Black will tell JC to get on the helicopter in a more stern tone of voice as they rebuke him for his interference.
---> '''Man In Black''' (If JC does not eavesdrop on Walton): "You may use the helicopter, Mr. Denton. Simons appreciates your respect for his interrogation of the prisoners."
---> '''Man In Black''' (If JC eavesdrops on, or interferes with Walton's interrogation): "Get on the helicopter, Mr. Denton. Simons did not appreciate your interference."
*** Simons also has lines for when JC enters the cell and attempts to interrogate the prisoners himself, and Simons also has an additional line for if JC kills a prisoner.

* During the second visit to Prague, you can find and take out Radich Nikoladze (the head of the Dvali crime family), despite nothing telling you otherwise. Doing so causes Otar to take over the Dvalis, and he is the one who is encountered near the end of the "Hunting Down The Final Clues" mission. Even better, if you do all of Otar's requests and take out Radich before arriving in Prague for the third time, he will be much more friendly and welcoming when you go to the theater to get information on the shipment.

* Entire game:

** The game has a shocking amount of contexutal dialogue depending on the order you complete objectives in. As one example, late in the game you stop off at Morgan Everett's house to get filled in on what to do next. When you leave to go to the helipad, you encounter a weird mechanic who seems shady. Talking to Everett reveals [[spoiler: the mechanic is an MJ12 plant sent to take out JC before he goes to the next location. Taking him out has JC explain the situation to his pilot, Jock. However, if you ignore Everett and just kill the mechanic outright, JC will say he didn't trust the mechanic and took him out as a precaution]]. This level of detail is ''everywhere.''

** Going all the way back to Everett after meeting and/or dealing with the "odd mechanic" results in a bit of dialogue where JC informs Everett of the odd guy, while Morgan believes he just met Pierre, his mechanic and is glad to know he's okay. JC then mentions how the guy was NotEvenBotheringWithTheAccent, which makes Everett just as suspicious. JC will also inform he's been taken out if the player did so, which Everett thanks him for before he starts wondering how the fake could have actually gotten as far as he did.

The ''VideoGame/DeusEx'' series is chock full of this.

** All of the UNATCO troopers deployed on the island once Leo Gold is captured/killed are invulnerable ... ''except'' for the one walking up the stairs at the top of the statue. Taking him down nets you a free assault rifle early, and it also explains why assault rifle ammo can be picked up in Battery Park (you normally don't get an assault rifle until you reach Hell's Kitchen). Manderley also has alternate dialogue based on whether the player knocked out or killed the soldier in the briefing afterwards.
** If you finish the Statue of Liberty mission without visiting Harley Filben first, then go back to talk with him after you detain Leo Gold, Filben asks why he stood around for an hour if no one wanted to talk to him, while JC tells him he found a back door into the statue. Filben then insists that he wants extra pay, and JC tells him to take it up with Manderley. JC will also apologize to Filben again when you meet him later on at Battery Park Station.
*** Filben will also be especially upset if the player killed Leo Gold, since, as Filben explains, Leo was his primary source of information.

--> '''Man In Black''' (If JC does not eavesdrop on Walton): "You may use the helicopter, Mr. Denton. Simons appreciates your respect for his interrogation of the prisoners."
--> '''Man In Black''' (If JC eavesdrops on, or interferes with Walton's interrogation): "Get on the helicopter, Mr. Denton. Simons did not appreciate your interference."
*** Simons also has lines he says when JC enters the cell and attempts to interrogate the prisoners himself, and Simons also has an additional line for if JC kills a prisoner.

** Renault's dialogue in the hostel changes if the player raided the nearby bakery and stolen the zyme before talking to him. Instead of trying to negotiate, Renault just cuts to the chase. The nearby bartender's dialogue also changes depending on whether JC already talked to Renault, and whether they met Nicolette behind the club or not.

* The mission at Mako Ballistics to either find, analyze and register the prototype of a Rail Gun for the WTO or kill the lead scientist for the Order. This is usually mutually exclusive because opening the canopy for the weapon closes the door to the scientist and killing him first will disable the switch to open the canopy in the first place. You can however trick the door by placing one of the boxes on the floor underneath the door, forcing it to stay open when it would normally close. Analyze the gun (netting you a "mission accomplished" from the WTO and a bonus later on), then go to the scientist. You'll need a ammo-free weapon like a knife or blade to kill him because his health is abnormally high at this point. When finally killing him, you'll receive a "mission accomplished but it was too late" instead of a normal "mission accomplished" from the Order and later on you are chewed for still helping the WTO. Bonus points for that regardless, you get the Order's bonus later on as well.
** Later on, you get the option of killing the security chief in the Arcology, or letting him live so he'll give you the code to activate the nanobots for the plague cure. It's entirely possible to do both, as depending on which missions you did beforehand, the chief will still be in his office even after you activate the bots, so you can cure the plague, go kill him afterwards and get your reward from the harvester.
** NPC's will keep track of your actions, if you kill schoolgirls at Tarsus Academy, Donna Morgan will chew you out over it. You can kill most [=NPCs=], which will automatically complete their missions. You can get rewards from other characters that aren't listed as missions-If you talk to Dr. Nassif after you find his daughter, he'll give you 200 credits (and if you killed Silas, Alex will mention that and Nassif will ask you if you're sure Silas was behind the disappearances); and after you bribe the manager of NG Resonance to endorse Peequods or Queequegs, you can tell NG about her manager taking bribes and you'll get 200 credits for it.
*** There's also a hidden ending which you can get by flushing the UN flag in the toilet, which opens up a dance room with all the characters and comments from developers are seen floating around the room.
* Klara Sparks wants you to be non-lethal. However, you can still do lethal takedowns and not piss her off if you do it ''without her seeing you''. Oops, how did that corpse get there?

** Although Paul tells you to run during the 'Ton Hotel raid, and you can escape through the bedroom window, this will result in Paul automatically dying. However, if you stay and take out all of the attackers (or you get "killed" during the ensuing assault), Paul will survive and have extra dialogue talking about how he plans to get Smuggler to help him leave New York. This also impacts the rest of the game -- Paul will eventually make it to New York and have additional dialogue talking about how he needs to recover from the killswitch and the situation in UNATCO, then appearing at the end of the game to give JC some additional advice about which course of action to take in Area 51.

** Stephanie has additional dialogue if you go back up to the roof and talk to her after destroying the four sentry bots, despite there being no other reason to visit.

** The homeless people outside the MJ12-run gas station will give different dialogue if you wait to talk to them until after rescuing Tiffany.
** One of the scientists in the Ocean Lab will acknowledge the player's use of swimming through the Karkian tank and exiting next to her while entering for the first time, even though this is impossible without clipping through the base into the appropriate area.
** If you choose to redirect the missile and kill Howard Strong in the silo before doubling back all the way to the washroom to rescue the imprisoned scientist, JC and the scientist will have an alternate conversation where he tells the latter about what's happened and promises to stop Page once and for all.

** NPC's will keep track of your actions, if you kill schoolgirls at Tarsus Academy, Donna Morgan will chew you out over it. You can kill most [=NPCs=], which will automatically complete their missions. You can get rewards from other characters that aren't listed as missions-If you talk to Dr. Nassif after you find his daughter, he'll give you 200 credits(and if you killed Silas, Alex will mention that and Nassif will ask you if you're sure Silas was behind the disappearances); and after you bribe the manager of NG Resonance to endorse Peequods or Queequegs, you can tell NG about her manager taking bribes and you'll get 200 credits for it.

** In the prologue, if you wait around an unreasonable amount of time, the Gold Masks will steal the helicopter and take off. Instead of presenting a NonStandardGameOver, however, the plot continues, with the tone of the following cutscene (the Illuminati meeting) and the dialogue at [=TF29=] takes on a decidedly-different tone.

** An instance of this phenomenon that was never [[DummiedOut properly implemented]] would have involved the player being given the ability to go ''all the way back'' to Battery Park after destroying the generator in Hell's Kitchen, ignoring Gunther, Jock and the situation altogether (while Alex asks what JC is doing). If you go all the way back to the dock you started from, the boat pilot would have unique dialogue (talking about "needing to go" because of a situation that's developed) and would function as a hidden exit point. The triggers for this still exist in the game, but are unimplemented.

** Although Paul tells you to run during the 'Ton Hotel raid, and you can escape through the bedroom window, this will result in Paul automatically dying. However, if you stay and take out all of the attackers (or you get "killed" during the ensuing assault), Paul will survive and have extra dialogue talking about how he plans to get Smuggler to help him leave New York.

* In ''The Missing Link'', [[spoiler:Keitner]] will say different dialogue depending on how you dealt with the soldiers on your way to the person who set you free: If you kill a lot, she'll call you out. If you [[TapOnTheHead knock a bunch out]], she'll criticize you for [[RealityEnsues putting her men into comas]]. If you remain out of combat entirely, she compliments your "ghost" routine, and encourages you to keep it up.

* If you wait too long at Sarif Industries before going to the first mission, assuming that it's a video game and [[TakeYourTime the mission won't start until you start it]], ''the hostages will be dead before you even get there''. Even better is that several characters will chew you out after the mission for waiting.

** If you do this instead of speaking to Tong the next time you see him he won't mention that the two of your are supposed to be friends.

** Choosing to avoid contact with cops when you're asked to retrieve the data drive for Smiley from Ruzicka Station not only results in several [=TF29=] employees being friendlier towards, but Miller is genuinely nice. Compare this to the outcome most players will have, which is Miller chewing them out and getting angry.

** The game will acknowledge the use of glitches. Throw a Gas Grenade at UNATCO's front door, then run past the guard that comes out. Once inside, a guard will ''actually acknowledge you skipped a bunch of terrorists that way''. The game continues normally as if you just finished the first level legitimately, but not before acknowledging your ingenuity.

** If you barge into the women's bathroom during your first visit to UNATCO, Manderley chastises you for it later. (''VideoGame/MassEffect2'' has since done so as well.) The woman you encounter, Shannon, will also behave differently toward you for the rest of the game. If you don't go in, then she generally acts civil and friendly. But if you do into the bathroom, she'll never let you hear the end of it for the next few missions. In your first meeting with Manderley, he will reprimand JC on his intrusion into the women's bathroom as "unprofessional".