Jack learns the Grail is actually fake, but takes it anyway (SItuational Irony)
Jack breaks into the architect's apartment on the Upper East Side in hopes of retrieving the Grail and bringing it back to revive Parry. When he picks it up, he notices that there is an engraving on it—it was a gift to the architect as a child—that reveals that it is only a trophy, not a grail at all. For a moment, it seems that this will deflate Jack's belief in his mission, but it does not, and he takes the "Grail" with the purposefulness of a knight. This situation is ironic because Jack has been so skeptical about Parry's magical thinking throughout the film, and now that he finally has confirmation of Parry's grand delusions, he doesn't care and he believes in it. While the viewer expects the realization that the Grail is fake to be more disappointing, it has no bearing on Jack's mission.
Lydia's Membership (Dramatic Irony)
In order to set Parry up with Lydia, Jack stages an elaborate charade where he tells Lydia that she has won a free promotional membership to the video store. He calls her, then sends the homeless cabaret singer to deliver a singing telegram to her office. Lydia eventually agrees to come to the store, and then agrees to a plan to come over to Anne's apartment and get her nails done. While the whole arrangement is meant to set Lydia up with Parry, she has no idea that this is the plan. Thus, there is a tension between the fact that the viewer knows about the matchmaking, but Lydia does not.
Parry's Delusions (Dramatic Irony)
There is a unique kind of dramatic irony at play in the fact that Parry is so delusional and disconnected from reality. While Jack and the viewer know the facts of Parry's situation, he truly believes himself to be a medieval knight. Thus, there is a dramatic irony between the fact that we know Parry's true identity and Parry does not. This is not a traditional dramatic irony, however, because Parry does know his real identity somewhere in his mind, but has buried it for self-preservation. The disparity between our knowledge and his is due to his own post-traumatic psychological processes, not due to an actually limited access to information.
Parry was a victim of the shooting (Situational Irony)
One of the most prominent instances of irony in The Fisher King is the fact that in the moment that Jack is about to be killed by some bum-hating teenagers, the person who saves him is Parry, a man who was hurt by the shooting at Babbitt's three years earlier. This coincidence is ironic because of all the people to come to Jack's rescue in a near-death moment, it is someone who feels hurt by an instance of violence for which Jack feels personally responsible. Their interconnectedness is random enough to feel ironic, and they become entangled in one another's lives in such a way that neither Jack nor anyone would have ever expected.
