British actor David Niven was already a well-known leading man in Hollywood in 1939, when he suspended his acting career to fight for his country in World War II. He served in the General Headquarters Liaison Regiment, also known as “Phantom,” a secretive reconnaissance unit.
Niven was present at the Battle of the Bulge, and was once stopped by American soldiers. The Americans were on edge due to (true) rumors of German infiltrators wearing Allied uniforms, and were trying to ferret out the saboteurs by asking everyone trivia questions. Some soldiers who encountered Niven asked him who won the 1943 World Series. The British actor, who didn’t follow baseball, replied "Haven't the foggiest idea, but I did co-star with Ginger Rogers in ‘Bachelor Mother’!” The Americans only then noticed who he was and let him pass.
He could have fared worse: during the same battle, British General Bernard Law Montgomery had a tire on his jeep shot out by a twitchy American soldier who had heard rumors of a German Montgomery-lookalike going around giving false orders.