There’s an internet rumor that is not entirely unreliably sourced*: George Lindsey, the actor who is most famous for playing the role of Goober Pyle on The Andy Griffith Show, was offered the role of Spock before it was given to Leonard Nimoy.
MeTV asserts that in a 2006 interview upon the 40th anniversary of Star Trek, Nimoy said that Gene Roddenberry offered the role to Lindsey. In his autobiography, actor Earnest Borgnine wrote that Lindsey, his friend, was definitely offered the chance to play Spock.
I’d like to see some more sourcing on the claim, hopefully from the late George Lindsey or Gene Roddenberry themselves, but have been unable to do so.
I do, though, believe that Lindsey was up to the task. Although he was famous for playing the bumbling, dim-witted Goober, I recall a 1963 episode of The Rifleman in which Lindsey guest starred as an ex-con. In an impressive scene, Lindsey convincingly depicts a sexual predator looking forward to his next hunt. I’m convinced that Lindsey’s acting range could have handled the role of Spock.
*I’m a librarian, so I have to talk this way.