Near the beginning of the episode, the imposter is talking with Sgt Saunders squad and he has a cigarette in his mouth. When he turns to walk off, the cigarette is in his hand.
Lt. Hanley was ready to lead the men on special assignment from the shack and said "Caje, take the point and Peabody, bring up the rear" (instead of saying Littlejohn bring up the rear.) Dick Peabody plays Littlejohn. For a couple seconds, Dick Peabody starts to grin, thinking the director will yell "Cut!", then stays in character to continue the scene.
In one scene Lt. Hanley addresses Litllejohn using the actor's (Dick Peabody) real last name - "Peabody, bring up the rear."
When the men find Red, the dead American GI that was dressed in a German uniform, Red's eyes keep fluttering.