These are from a trove of recently found genuine WWII German jokes, which was a mild form of resistance in the Reich. I'm pretty sure these are not recent fakes
"Hitler visits a lunatic asylum, where the patients all dutifully perform the German greeting. Suddenly, Hitler sees one man whose arm is not raised. "Why don't you greet me the same way as everyone else," he hisses at the man. The man answers: "My Führer, I'm an orderly. I'm not crazy!"