There's never been a tv show where 90% of the cast were visually apparent aliens in an interplanetary/interstellar community.
There was this
exchange crewman wearing some equipment to help him breath while on the Enterprise-D from the Season 2 episode "A Matter of Honor".
In the rec room scene ifrom ST:TMP, there was (iirc) a crewmember with a mask that covered his entire face. Must be a very isolating.
Mr. Laser Beam wrote:
As for the T'Kumbra: I still believe that Solok could have used his influence at Starfleet Command in order to populate his ship with an all-Vulcan crew. That way, he gets the best of both worlds: he gets to serve in Starfleet, but not alongside "filthy humans".
If Captain Solok was able to fill his command staff with Vulcans who harboured similar view to his own, then any non-Vulcan who was hapless enough to be assigned to Solok's ship could find their lives (both on duty and off) so unpleasent and down right objectionable, that they would soon formally request a transfer. A request that Captain Solok would swiftly authorize.
But only after Solok publically berated the crewmember for request one in the first place.