The projector Klinger is running blows up before the rain from the leaky ceiling begins pouring onto it.
When Margaret is showing Frank her flask of brandy, Loretta Swit's fingernails can be seen to be over an inch long. No nurse, especially a head nurse, would have fingernails that long.
Previously, in "Officers Only" Frank brags to Hawkeye and Trapper that he pulled some strings with General Hammond and got the officers club put in while they were away in Tokyo. He's even seen inside with Margaret drinking Shirley Temples. Yet, as soon as Frank is left in charge while Henry is away for a week, he boards up the officers club, takes the still out of the swamp, and essentially bans all alcoholic beverages in camp due to his extreme dislike of drinking.
However, Frank's impetus for the "Officers Only" Club was to keep out the enlisted, whom Hawkeye and Trapper got permissible entry for by bringing in the general's son, much to the dismay of Frank. It wasn't about the alcohol. It was about exclusivity. Thus, closing the club carried no weight in Frank's mind because his dream of it was already shattered.
However, Frank's impetus for the "Officers Only" Club was to keep out the enlisted, whom Hawkeye and Trapper got permissible entry for by bringing in the general's son, much to the dismay of Frank. It wasn't about the alcohol. It was about exclusivity. Thus, closing the club carried no weight in Frank's mind because his dream of it was already shattered.
(at around 6 mins) When Father Mulcahy is praying, the set is visible in the background above the tent at the top left hand side of the screen. The light shining down onto Mulcahy is obviously from a spot light as well.