The first season of MASH struggles to find the right tone, and writers don't have the character history to rely on in making seriously emotional episodes. There are some very effective ones in the first season, even episodes before this one. But this is the episode where everything works perfectly for the first time. Aside from the very careful wordplay, there's an absurdist undercurrent. A fairly simple premise is built on, and spirals into a bigger production. It's wonderfully satisfying.
My favorite thing is a single, strange joke that Radar has, regarding his imaginary friend. One of the strangest things that the show ever did.