My thoughts about the Severance departments (WARNING: SEVERANCE SPOILERS!)
I think it's interesting how all of the departments shown so far seem to be related to Gemma/the Testing Floor. MDR is the most important one, actually working on the files that correlate to the rooms Gemma enters. However, O&D is shown to 3D print the objects she uses and encounters in each room. And, Mammalians Nurturable exists for the purpose of raising goats to be sacrificed whenever someone from the Testing Floor is killed. (Which suggests that Gemma is not the only test subject who is/has been kept prisoner on the Testing Floor. Why would they have a whole department dedicated to raising a ton of goats if they only needed to sacrifice one for Gemma and Gemma only? This somewhat supports my theory that Dylan, Irving, and maybe even Helly are refining data related to other test subjects. These other three test subjects would probably be people they love, who they believe have died. Petey and any other past MDR refiners would then have been refining even more test subjects.) It's hard to say what purpose Choreography and Merriment may have in relation to Gemma and the Testing Floor. However, maybe they play music in some of the rooms Gemma (or once again, any other test subjects who may or may not exist) enters?
Obviously, Gemma and any other possible test subjects are a very important part of Lumon, but the fact that every department seems to exist specifically to make/do something in relation to the Testing Floor shows just how important the Testing Floor is. At least so far, it doesn't seem like the departments exist for any reason BESIDES contributing to the Testing Floor in some shape or form. It's not like O&D is 3D printing objects to be sold to the public or something. And it's not like MDR is refining data for any other reason besides for creating the testing rooms. It makes me wonder why, specifically, Lumon is holding test subjects at all. Maybe it has something to do with reviving Kier? It's clearly something big if they're hiring all of these severed workers for the pure sake of contributing to the test subjects and the test rooms.
