In the opening scene, as Colonel Klink is bragging on the successes of the Third Reich, the prisoners are muttering. Newkirk clearly says, "rhubarb rhubarb". That is sort of an actor's in-joke. In the early days of British radio, TV, and movies, crowd muttering scenes often had the extras repeating "rhubarb", "peas and carrots" or other nonsense words to simulate background dialogue.
The captured "Tiger Tank" looks nothing like an actual German Tiger tank. It's actually a U. S. made M7 self-propelled howitzer, not a tank. After WWII, almost all Tiger tanks were destroyed. There would not have been one available for a TV show to use.
Werner Klemperer (as Klink) is just getting used to wearing the monocle. During the scene where Hogan is protesting the interrogation of his men by a Gestapo Officer, it takes three tries for Klink to get the monocle in place properly.
This is one of the few early episodes in which LeBeau wears a blue sweater. For the rest of the series, his sweater was red.