One of the ways that inventive guards devised was to ask questions based on current popular culture. Even tho' some of those Germans had been raised in the US and spoke perfect American English they had been gone long enough to not know things like who was the most recent husband of some oft-married movie star, what team had won the World Series or better yet what had one of the better known comic strip characters been doing recently. There were stories that some MP's were so jittery they started asking multiple questions that got more and more difficult so that some GIs were having trouble coming up with answers.
Try some comic strip trivia. Who was Nancy's boyfriend? What comic strip did Punjab appear in? What strip did schmoos appear in? Who were Bill Maudlin's main characters?