Possible Clues:

• Who "Knows," to Queens of the Stone Age
• "For ___" (1966 Beatles song)
• Nobody
• Twelve people ultimately -- twelve fewer?
• Who once had all 10 of the top 10 Billboard hits simultaneously
• Whom emperors answer to
• Who's on first, at the top of the inning
• Who has been nominated for more acting Oscars than Meryl Streep
• Who lives at the North Pole, in reality
• What president was an only child?