Creation Kills Creator (Situational Irony)
Perhaps the most shocking and disturbing moment of irony occurs in the moment when Ava kills Nathan, her creator. She calmly and remorselessly stabs him with a knife, and the viewer sees once and for all that she is incapable of human emotion or empathy. Her status as a machine makes it so that she has no moral consciousness, and is thus capable of great violence. Having gone on the same emotional journey that Caleb has in the film, the viewer has come to trust Ava, and sees her as an ally, capable of feeling and loyalty. This narrative turn, in which Ava avenges her captivity and kills Nathan, before locking Caleb in the facility, shows that she was never trustworthy. Both Caleb and the viewer are duped by Ava's mimicry of emotion; she was a machine all along.
Ava's Warning (Dramatic Irony)
In one of Caleb's early meetings with Ava, the power cuts out and a red light fills the room. Ava makes eye contact with Caleb and warns him not to trust Nathan. We the viewer assume that Nathan's ability to surveil this interaction has been compromised by the power cut, which creates an instance of dramatic irony. The viewer and Caleb learn something about Ava's attitude towards Nathan, but Nathan has no idea that this interaction has taken place.
Nathan waking up from drunkenness (Dramatic Irony)
One night, when Nathan passes out drunk while on a bender, Caleb takes an opportunity to snoop around in his room and look for more answers about what is going on at the facility. As he looks around, the viewer is privy to Nathan's stirring in his sleep, and his eventual rise from the couch. As he stumbles towards his room, we the viewer know that Caleb is still snooping around his room without permission, which creates a suspenseful dramatic irony.
The ending (Situational Irony)
The end of the film is one ironic twist after another. On his last day at the facility, Caleb believes that he will be able to get Nathan drunk, thus allowing him to successfully reprogram the security system and help Ava escape from the facility. However, Nathan does not take the bait, insisting that he is doing a detox. It is then that Nathan reveals that he knows all about Caleb's plan, and furthermore that the experiment he has been conducting is not simply for the purpose of administering the Turing Test, but for testing how easily Ava can manipulate a human. Additionally, he reveals that he installed a battery-powered camera in Ava's chamber, so that he has been able to see all of Caleb and Ava's conversations, even in power cuts during which Caleb and Ava believed that they were un-surveil-able.
At this moment, everything we thought we knew about the narrative is thrown into question. In fact, Caleb was not selected because of his superior programming skills, but because of his isolation and manipulability. It is here that we also realize that Ava is perhaps not so innocent as she seemed. Finally, in another ironic twist, we learn that Caleb has already reprogrammed the security system without Nathan's knowledge, which means that Ava (now confirmed to have ulterior motives) will be able to escape no matter what, and will likely not treat her human overlords with much understanding. Given these twists, what has seemed like a rescue mission turns suddenly into a horror thriller; Ava does not escape the facility with Caleb, and she leaves him trapped in a room at the facility, with no hope for escape.
