The reason a person who believes he sees a woman when in reality he is looking at a gourd is called crazy is because this is something beyond usual experience. However, when a person thinks his wife, who is enjoyed by many, to be an ever-faithful Penelope, he is not called insane at all, because people know that this is a common thing in marriage.
We’ve all done it: hollered a confident “hi, Mark!” to a guy named Greg; slipped up and called our sixth grade teacher “Mom”; snuck up on our sister from behind and delivered a pinch, only to realize she was a stranger. These kinds of gaffes are simultaneously the most mundane and most embarrassing of mistakes. More people than I can count told me stories like these, all of which ended with the speaker expressing the fervent desire to vanish. As one such person put it, “The only thing you can say in these situations is, ‘Sorry, I just had a brain biopsy.’”