From 1982 to 1986, the Nickelodeon network hosted an educational program called Standby: Lights! Camera! Action!. It showed how movie productions function. Leonard Nimoy, who played Spock on Star Trek, hosted it. This clip from a 1983 episode shows how prop makers and costumers made the non-human characters in Return of the Jedi.
It's a pity that George Lucas did not make full use of the acting talents of the Star Trek cast in Star Wars. He could have simply imported the entire cast and set them to work from Episode IV onward.
-via Geek with Curves