Funny Thing Happened on the Way to London - S3-E5
Plot hole: When the driver of the car addresses Roberts (the real Roberts that is, not the double), Roberts reprimands him, telling him not to call him Baumann. It is safe to assume the guard was supposed to be speaking German, since he addressed Roberts by his German identity. That poses some interesting questions. Did Roberts speak English? In those days, most Germans did not even have a basic knowledge of the English language. Did he speak German? That would imply he has a good enough command of the German language to pass as a German. Roberts however isn't a spy like Hogan and his crew, but a pilot in the RAF.
Funny Thing Happened on the Way to London - S3-E5
Other mistake: When Lieutenant Bauman starts speaking German, his last two words "especial mission" is said in a decidedly French accent. The correct German phrase would be "Sonderauftrag." Non-German terms like "Mission" were generally avoided in the Wehrmacht for ideological reasons.
Funny Thing Happened on the Way to London - S3-E5
Revealing mistake: When the staff car enters the camp, you see a set of tire tracks leading up to, and stopping at, Klink's position. When the car comes in, it precisely follows the tracks, suggesting previous takes.
Answer: It's a solitary cell. Steve McQueen, star of 'The Great Escape' is known as the 'Cooler King'.