The Kims' credentials (Dramatic Irony)
The Kims' entire path to employment in the Parks' house is based in a deception. Each of them pretend to be highly qualified for the position in question, and do not disclose their relation to one another. Thus, their employment in the house creates a heightened instance of dramatic irony, in which we know something the Parks do not.
Moon-gwang and the driver's dismissals (Dramatic Irony)
The Kims manipulate the Parks into firing both the housekeeper and the driver, so that Ki-taek and Chung-sook can take over the positions. In this situation, the viewer knows that the Kims are fabricating the rationales for the firings, but the Parks do not. Additionally, neither Moon-gwang nor the driver know why they are getting fired, but the viewer does.
The Kims are inside the house (Dramatic Irony)
When the Parks return home unexpectedly from their camping trip, they have no idea about the violence or the decadence that has taken place in their home. As far as they know, Chung-sook has been quietly tending the home while they were away. The viewer knows that it was quite the contrary, however, and that not only are Moon-gwang and Geun-sae trapped in the underground bunker (about which the Parks know nothing), but the Kims are still there as well, hiding in various locations, waiting for the Parks to go to bed.
Geun-sae the ghost (Situational Irony)
A rather darkly humorous irony occurs when Geun-sae emerges from the basement into Da-song's party, wielding a kitchen knife with his face covered with blood. We know that Da-song is traumatized from seeing Geun-sae a few years earlier on his birthday and believing him to be a ghost, and this birthday is meant to help him recover from that trauma. Just as Da-song goes to blow out his "trauma recovery cake," that same "ghost," Geun-sae, runs into the party and stabs his art therapist in the chest.
