There is a pervasive sense of black humour that runs throughout this brilliant short story that says so much about the alienation facing the common man in life. First of all, let us remember the way that ironically the metamorphosis that Gregor experiences is actually shown to be an improvement to the rigours and frustrations of his life as a travelling salesman. Gregor is finally able to rest and to do what he wants to do without feeling forced into action to look after others.
Then there are other notes of humour, such as the charwoman who is employed by the family to tidy up, and her attitude towards Gregor. Note, for example, how she responds to finding an unmoving Gregor in the room:
Since she happened to be clutching the long broom, she tried to tickle him from the doorway. This had no effect, and so she grew annoyed and began poking Gregor. It was only upon shoving him from his place but meeting no resistance that she became alert. When the true state of affairs now dawned on the charwoman, her eyes bulged with amazement and she whistled to herself. But instead of dawdling there, she yanked the bedroom door open andhollered into the darkness: "Go and look, it's croaked; it's lying there, absolutely croaked!"
The way in which slang is used to refer to Gregor's demise, "it's croacked," certainly adds to the black humour of the situation whilst underscoring the plight of Gregor. The fact that his death brings his family such happiness, and that his metamorphosis is the necessary catalyst to change his family and make them exert themselves is at once darkly humorous and undescribably tragic.