Barry Atwater

 played Boris, one of Endora's Halloween party guests, in the third season episode, Twitch or Treat (1966).

Biography
Barry Atwater was an American actor and sound technician. He was a tall, sinewy, rather hard-faced character actor, ideally suited to play tough cops, gunslingers and even zombies. He was best known as the vampire Janos Skorzeny in the 'Kolchak' pilot movie The Night Stalker (1972) and the venerable father of Vulcan philosophy, Surak, in Star Trek: The Original Series (1966).

Atwater taught recording and mixing techniques at the UCLA sound department from 1948 to 1952. He had a small role in the Oscar-winning short student film A Time Out of War (1954) which led to acting on the stage and for television (from 1955).

Atwater died from a stroke eight days after his sixtieth birthday. He had been battling terminal cancer at the time of his death.

Source
Barry Atwater on the Internet Movie Database. Retrieved on March 18, 2020.