I went on a date once with a guy from my university's medical school. He looked completely normal, and I was having fun until we got to the restaurant and he launched into an endless diatribe about "those nasty Jews who have overtaken Hollywood and mass media to spread their propaganda and their values of greed and capitalist competition."
"Well, you know what they are like," my date concluded his impassioned speech.
"Oh yes, I do," I said. "I know exactly what they are like given that I see one of them every time I look in the mirror. By the way, I always pay for my own meal, but you made me remember that I'm a greedy Jew. So now I will go back to my friends to discuss our Jewish conspiracy to overtake the world, and you can pay the bill."
And then I left while he sat there in astonishment. I'm sure that now he is telling people that Jews are so sneaky that we often look in ways that makes it impossible to recognize us.