In Part 3, Blakely's Fork in the Road riddle, and The Reveal that he didn't actually know the answer to it is symbolic of his relationship with his crew. Blakely is in command of the crew, and flies the plane, but he can't possibly succeed in his mission without the contributions of his crew, in particular his navigator, Crosby.
Crosby: Hey, Blakely, what was the answer to that riddle?
Blakely: [lights a cigarette] I was hoping you’d tell me.
Bob being outed as a German infiltrator in Part 4 makes sense once you take a closer look at a few details. For one, he has no visible injuries on his face in contrast to Quinn and Bailey, who have visible burns and lacerations indicative of bailing out of a burning and crashing aircraft. Second, he gets the US National Anthem wrong. Thirdly, he writes the date on his test paper in the European style rather the American one. After executing him, the Belgian Resistance members get further confirmation by the fact that he has a German-model lighter. Parts 2 and 3 both have scenes of American airmen using American-brand Zippo lighters, establishing how common this model was among American servicemen.
In Part 9, Crosby confronts Clouter for failing to keep the equipment room open until all of the crews had gotten their gear, and then slams Clouter's face down into his food for his insubordinate response. The whole time, Major Blakely, who used to fly with Crosby and is one of the few remaining original members of the Bloody Hundredth, silently watches the interaction before calmly tapping Crosby on the shoulder to get him to stop. Crosby and Blakely are two of the few remaining original members of the Bloody Hundredth, and have flown together through some harrowing missions. They trust each other enough that Blakely is willing to let Crosby discipline an insubordinate junior officer as he sees fit, and that Blakely can calm Crosby down with ease once he's made his point.
Buck is repeatedly established to have no interest in or knowledge of team sports, such as baseball. When the Belgian Resistance members interrogate downed American airmen, they include a trick baseball question. They are also established to decisively execute those who fail their test. Had Buck been captured by Belgian Resistance, he might have failed the baseball question and been executed. One must wonder how many Americans got mistakenly executed as spies for failing to know some basic Americana.
