Famous story that may have never happened or may have happened hundreds of times is when asking such a person something Judaism related they would respond "how do you know I'm Jewish"
Heard once a joke, a chasidishe bucher decided to go otd he changed his look and went into a electronics shop and wants to buy the tv on display the owner answers him that he doesn't sell a tv to a chasidishe bucher,
He asks him how do you know I'm chasidish he answers because this thing on display is a microwave and not a tv.