Bertilak
The central irony of Sir Gawain and the Green Knight is that Bertilak and the Green Knight are one and the same. Gawain does not realize this until the end of the text, but the prevalence of tests, games, and challenges throughout the poem suggest a connection between the Green Knight and the lord of the castle.
The Girdle
Gawain accepts the girdle from Lady Bertilak because he is afraid the Green Knight will injure or kill him. Ironically, it is Gawain's possession of the girdle that leads the Green Knight to stroke him, because Gawain failed to disclose to the Green Knight that he had the girdle on. In reality, it is honesty that would have saved Gawain from the Green Knight's blow.
Chivalry
Some critics argue that Sir Gawain and the Green Knight maintains an ironic tone toward chivalry and the chivalric code that knights must uphold. Through Gawain's "failures" in the face of the Green Knight and the various challenges he lodges at him, one could intuit that the author of the text perceives the demands of chivalry as ultimately impossible to fulfill.
Parallel Hunts
While staying at Bertilak's castle, Gawain declines the opportunity to participate in the hunting and butchering led by Bertilak and his men. Ironically, however, this choice leads Gawain to take part in a "hunt" all his own – only this time, he is the one being hunted, as Lady Bertilak pursues him romantically as a test of his willpower and fidelity.
