Clytemnestra's Words to Her Son (Dramatic Irony)
When Clytemnestra comes to her daughter and instructs her to show up at the rite, she also meets "Philebus" and tells him point-blank, "Leave this place. I feel that you are going to bring disaster on us" (71). This is ironic given the fact that the readers know exactly who this young man is and, even at this point before he's decided on it definitely, what he plans to do. He is more dangerous than Clytemnestra could possibly imagine.
Zeus and Orestes (Dramatic Irony)
One of the more sustained uses of dramatic irony in the play is the dialogue between "Demetrios" and "Philebus." Readers know both of these characters' actual identities are but neither of them is quite sure of the other in the beginning of the play. Orestes thinks Zeus is Demetrios, though Orestes's tutor warns him that the bearded man is not who he seems. Zeus thinks Orestes is Philebus, though he also guesses at the young man's identity.
Freedom (Situational Irony)
There is a great deal of irony in Orestes' experience of freedom, which of course means that there is an irony in Sartre's existentialist philosophy. Orestes is free; he does not need to listen to god or man. He does what is right and just, lives only in the present, and is liberated from false belief systems. However, he is not happy and considers this freedom a burden. Anguish is the bedfellow of freedom, not peace.
Electra (Situational Irony)
Electra is vengeful, bold, and full of vitriol. She dreams and rages and obsesses over the return of her brother so he can dispose of her mother and the usurper king. Readers are prepared to see Electra's pleasure and fulfillment after the deed is done, but are instead confronted with the irony of Electra's confusion, fear, and revulsion. While such feelings may not be unexpected for most people, for Electra they are, given her fifteen-year commitment to revenge and her flagrant display of disobedience and autonomy in front of the Argives at the rite. Thus, it is ironic that she mentally collapses as a result of Orestes' action.