Was Cantor Surprised? published in Monthly is debunking (or trying to do so) that Cantor was so surprised when he discovered $I=[0,1]$ and $I^2$ have the same cardinality that he said “I see it, but I don’t believe it!”. The abstract of the paper reads as follows:

Abstract. We look at the circumstances and context of Cantor’s famous remark, “I see it, but I don’t believe it.” We argue that, rather than denoting astonishment at his result, the remark pointed to Cantor’s worry about the correctness of his proof.