> the General (Colonel?) is flabbergasted to find out that Oppenheimer has a Christmas tree in his living room ... xD

Well, you seem to be in the right place to know about Christmas Trees:

Modern Christmas trees emerged in western Germany during the 16th century as Christians brought trees into their homes and decorated them with gingerbread, nuts and apples

Imagining LanX now, wearing Lederhosen, while eating gingerbread, nuts and apples under the Christmas tree. Sorry, couldn't resist. :) Do you ever wear Lederhosen BTW?

> the mini-series is available on youtube

Thanks! Watching now. Near the end of Episode 3 (at the 53:55 minute mark) there's a conversation between General Groves and Oppie in Oppie's new Los Alamos office:

Groves: I was wondering, do you actually celebrate Christmas? well, I mean you being different, well, Jewish?
Oppie: We have a tree
Groves: Good, I was wondering if you'd put that under it for me? (he hands Oppie a Christmas present)

LanX, is that the scene you remembered?

This mini-series lays bare the stark difference between Scientific and Military Culture ... hmmmm, given my first job was in Defence Science (where I experienced both cultures first hand), the logical next episode in this series seems to be Military Organizational Culture. :)