Elisa the Mute (Situational Irony)
Even though Elisa cannot speak, she expresses some of the most profound thoughts in the movie and uses sign language to get deep to the core of the other characters. Through simple signs for egg, music, and you and me, together, Elisa courts a creature that isn't even the same species as her. On the other side of the spectrum, Elisa gets under Strickland's skin by signing fuck you to him while he's in the middle of his stressful investigation. The only time we get a real monologue from Elisa (as translated by Giles), it's a heart-wrenching plea to rescue the creature that ultimately wins both Giles and the audience over.
"I think this is some of my best work" (Verbal Irony)
Repeated by Giles several times throughout the film, we first hear this line when he's trying to convince himself that he likes his illustrated ads for Jello. The last time he says the line is the most hilarious instance, though, as he calls the forgery he makes of an ID card to help him gain entrance to the laboratory some of his best work. It's ironic since he's calling a forgery his best artistic output and, as we learn later, because it actually isn't even an effective forgery.
Elisa and Zelda are Dismissed (Dramatic Irony)
At the beginning of his investigation into the disappearance of the asset, Strickland calls Elisa and Zelda into his office. He interrogates them for a bit before getting frustrated and beginning to demean them, asking himself why he's asking for tips from "the fucking help." He tells them they're dismissed, and we know that Strickland is in for some trouble if he has zero idea that Elisa is the culprit. It comes off as especially ironic, since it's clear he's too interested in her sexually to notice she may have been the one to seduce and kidnap the creature.
The Butter Cake (Situational Irony)
When Hoffstetler's contacts come to his apartment—catching him in his underwear—to discuss his potential extraction from his espionage role, he offers them a slice of butter cake. One of them accepts. We see in this scene that Hoffstetler fears he will be shot right then and there, and his show of hospitality is actually an excuse for him to grab a knife in the event he has to defend himself. To further the irony, the thug who seems like he would be the one to do the deed (and later in fact does shoot Hoffstetler) absolutely loves the butter cake.
