It's only recently occured to me how the Heroes almost never reached a first-name basis with each other, even in spite of their obvious camaraderie. Granted, they still addressed Hogan by his rank, out of a clear sign of both respect for him and military courtesy, but even so, just about none of them really exercized much in the way of military correctness (even Hogan himself was usually relaxed about such). I don't know how true to military life fictional television has ever been, but it seems like almost every military show I've ever seen, you could tell the closeness of the personnel by their use of their comrades' first names (or in some cases, like M*A*S*H, whatever nicknames they had) - and usually those who still addressed each other by their last names were shown to be rigid and by-the-book.
In the case of HH, the only characters I recall ever being addressed by their first names with any sort of regularity were LeBeau and Carter - in the latter's case, it's implied that was actually out of disrespect from his fellow Heroes because of what a goofball he could be and occasionally fouling up their plans as a result. None of them seemed to harbor any disrespect for LeBeau though. Speaking of LeBeau, one of the only times I can recall him even addressing Newkirk by his first name was "Cuisine a la Stalag 13" when he leaves the outfit to answer de Gaulle's call for all available Frenchmen to fight for their homeland.
Like I said, that's just an observation I've recently had.
