That slip of the tongue reminded me of my third favorite Orson Welles movie, "The Stranger", which took place in the fictional town of Harper, Connecticut.
I don't know who wrote the following, but it can be found on many sites around the Internet:
Welles is the Nazi war criminal Kindler hiding out in a small Connecticut town where he has become a valued member of the community known as Rankin.
Edward G Robinson, playing a good guy for a change, is the detective who tracks him down, and then has to prove who he is.
There's a wonderful bit of dialogue when his professorial Nazi character is fielding questions on the German character. Somebody asks him about Karl Marx to disprove a point.
"Ah, but Marx wasn't a German, he was a Jew," comes the telling response, delivered with such arrogance and conviction it makes you seethe.
It isn't until much later that government Nazi-hunter Wilson has a light-bulb moment and realizes that something is very amiss about what Rankin/Kindler said.