Rob Reiner has said he got a lot of roles early on because he looked like a Hippie but came to work sober with his lines memorized. Unlike many who looked the part at the time.
A pleasant surprise for me. Sometimes I look up actors to see how old they were in particular roles, and find out that I’m older now than they were then - but Burt Mustin really was old, having been born in 1884.
Babylon 5 had its Alien Corps, a troupe of actors who could emote well in latex that would play Minbari #5 one week and a Drazi assassin the next. The ambassadors on the Advisory Council were a recurrant role for some.
JMS generally had at least (and generally) one role for them without the prosthetics.
Suzie Plakson did well playing aliens:
She played four characters on various Star Trek series: a Vulcan, Doctor Selar, in “The Schizoid Man” ( Star Trek: The Next Generation ); the half-Klingon–half-human Ambassador K’Ehleyr in “The Emissary” ( Star Trek: The Next Generation ) and “Reunion” ( Star Trek: The Next Generation ); the Lady Q in “The Q and the Grey” ( Star Trek: Voyager ); and an Andorian, Tarah, in “Cease Fire” ( Star Trek: Enterprise ).