Cronauer initially may not have liked the idea of going out with Trinh's whole family, but he acquits himself very well, buying them gifts ("What's 1/18th of a dollar among friends?") and comforting Trinh when she seems a bit out of sorts and maybe a little aware of what Adrian might be after:
"Look... I know there's no way... but it doesn't mean we can't have a few laughs. I'll take whatever you can give because I'm happy just being with you."
Depending on your point of view, may double as a Tear Jerker, the short time Adrian spends in the village.
Definitely becomes one when Trinh bluntly refuses Adrian's friendship, even if we do know what he's after in the end.
She seemed to say that Vietnamese ladies, at least the kind she's trying to be, can't be friends with American men, on principle.
After Adrian's reinstated but still doesn't want to go back on, Garlick coerces Cronauer to do an impromptu radio show for a battalion full of soldiers on trucks; he realizes how much he enjoyed cutting up and having a good time on the radio, and figures the needs of the troops outweigh the risk of his being further punished for more irreverence.
Later, he dedicates Wonderful World to the troops he personally entertained; this becomes Soundtrack Dissonance and even a Tear Jerker when we realize we're most likely watching those troops accost and abuse (and in some cases, execute on suspicion of being Viet Cong) Vietnamese nationals at the same time we hear the song.
Definitely a Tear Jerker too: Adrian fulfills his promise to play softball with his class just before he's sent home.