The following is quoted from Hao Wang, Reflections on Kurt Gödel, p. 115f. I ran across it on a web site that no longer exists:
In connection with the interview for his US citizenship, he once told me that for this occasion he had studied how the Indians had come to America. Einstein and O.Morgenstern were his witnesses, and Morgenstern has told different people about aspects of the event. The following account is given by H-Zemanek and E.Köhler (see Zemanek’s report, Elektronische Rechenanlagen, vol. 5, 1978, pp. 209-211). Even though the routine examination G was to take was an easy matter, G prepared seriously for it and studied the US Constitution carefully. On the day before the interview G told Morgenstern that he had discovered a logical-legal possibility of transforming the United States into a dictatorship. Morgenstern saw that the hypothetical possibility and its likely remedy involved a complex chain of reasoning and was clearly not suitable for consideration at the interview. He urged G to keep quiet about his discovery.
The next morning Morgenstern drove Einstein and G from Princeton to Trenton. Einstein was informed; on the way he told one tale after another, to divert G from his Constitution-theoretical explanations, apparently with success. At the office in Trenton, the official in charge was Judge Philip Forman, who had inducted Einstein in 1940 and struck up a friendship with him. He greeted them warmly and invited all three to attend the (normally private) examination of G.
The judge began, ‘You have German citizenship up to now.’ G interrupted him, ‘Excuse me sir, Austrian.’ ‘Anyhow, the wicked dictator! but fortunately that is not possible in America.’ ‘On the contrary,’ G interjected, ‘I know how that can happen.’ All three joined forces to restrain G so as to turn to the routine examination.