Final answer:
The porter in Macbeth pretends to be opening the gates of hell, providing dark humor amidst the play's ongoing theme of treachery and murder.
Step-by-step explanation:
In Shakespeare's play Macbeth, the porter pretends to be opening the gates of hell rather than the gate to Macbeth's castle. This occurs in Act 2, Scene 3, when he equates the knocking at the door to knocking on the gate of hell, suggesting that he is the gatekeeper of the infernal region. This dark humor serves to contrast the dark and murderous actions taking place inside the castle, where Macbeth has just killed King Duncan.