Although many of Kafka's characters bear remarkable similarities to each other, the creature in "The Burrow" is especially similar to K., the Land-Surveyor in The Castle. This first struck me when I read in "The Burrow":
I shall dig a wide and carefully constructed trench in the direction of the noise and not cease from digging until, independent of all theories, I find the real cause of the noise. Then I shall eradicate it, if that is within my power, and if it is not, at least I shall know the truth. The truth will bring me either peace or despair, but whether the one or the other, it will be beyond doubt or question.1
The resemblance lies in the single-mindedness of the protagonists, for it is just this same trait that characterizes K.'s pursuit of the Castle. I have outlined this aspect of K.'s character in another essay, but certain examples may be useful. K.'s profession as Land-Surveyor is significant, for it typifies a mindset that is purely mechanistic, wanting to break everything down into its constituent parts, in order to construct a ladder of hierarchy by which to approach the Castle. In the same way, the creature formulates and discards theories as to what the noise's origin is. He is driving for the "centre" of the problem. As I have mentioned elsewhere, the Castle itself may not have a centre, and the noise has no discernible origin. The Castle is everywhere and at the same time is within K. The noise, likewise, is everywhere and thus seems to originate with the creature itself. Both protagonists are employing a system against their goal/problem that can only fail, since the goal/problem itself cannot be systematized.
A further similarity between the two works is actually a contrast. I read "The Burrow" as a sort of "Castle" story told from the inside. The creature is waiting inside a sort of Castle and is disturbed by what appears to be an intruder, the Beast. K. then would appear to be an intruder in the Castle. This would fit with Kafka's own description of his breakdown in 1922:
"Pursuit," indeed, is only a metaphor. I can also say, "assault on the last earthly frontier," an assault, moreover, launched from below, from mankind, and since this too is a metaphor, I can replace it by the metaphor of an assault from above, aimed at me from above.2
Kafka felt the conflict in both ways. He could identify with K. by describing the struggle as an assault from above, in which an inscrutable authority eludes him. He could also relate to the creature's fear of an intruder, an assault from below (ie. outside). That both protagonists are so similar only proves how much of a paradox is involved. The systems and resources they bring to bear on their situations are equally inappropriate, and although both stories were unfinished, there is an ominous feeling at the point where Kafka stopped writing them. In The Castle, it is the feeling that K. will never gain admittance, and in "The Burrow," that the intruder will in fact gain admittance and devour the creature. Both outcomes would leave the reader despairing, and perhaps Kafka himself felt this way and was unable to complete the stories for this very reason.
1Franz Kafka, "The Burrow," The Complete Stories, trans. Willa and Edwin Muir (New York: Schocken Books, 1971) 348.
2Franz Kafka, Diaries (New York: Schocken Books, n.d.) 202.