Possible Clues:

• Spock portrayer
• Spock player
• 'Star Trek IV' director
• Spock's portrayer
• "Star Trek" co-star of Shatner
• Longtime Shatner co-star
• Mr. Spock portrayer
• Leonard who played Spock
• Leonard who wrote 'I Am Not Spock'
• Vulcan portrayer