Originally Posted by Zardoz
He (Spock) was a suprise to all, including Nimoy. In fact, during season 2, fearing Spock would outshine Kirk (Who was the designated lead star) they started feilding other actors to replace Nimoy as Spock, amunst them David Carridine and Mark Leonard (Who ended up playing Spock's father!)"
Actually I think they were putting together lists of other actors because they feared they wouldn't be able to make a season-2 deal with Nimoy, who wanted to renegotiate his contract early due to the huge popularity of Spock in season one. (See "Inside Star Trek: The Real Story" by Herb Solow & Robert Justman, really fantastic insider account of the making of TOS.)