He's also well known (among physicists) for his precise and laconic utterance along with his exceedingly literal interpretation of others' sentences*. I just found out that there's a new biography of Dirac that claims that he was autistics. NPR has an interview of the author and there's an article about autism screening related to Dirac.
For many amusing anecdotes about the man, see this page.
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* For example (taken from the last link above), here is typical Dirac interaction:
When Paul Dirac made a rare error in an equation on the blackboard during a lecture one day, a couragous student raised his hand: "Professor Dirac," he declared, "I do not understand equation 2."When Dirac continued writing, the student, assuming that he had not been heard, raised his hand again and repeated his remark. Again Dirac merely continued writing..."Professor Dirac," another student finally interjected, "that man is asking a question." "Oh?" Dirac replied. "I thought he was making a statement."