Possible Clues:

• "___ the eggman!"
• "___ the Walrus" (Beatles song)
• Sum, sometimes
• Descartes's 'sum,' translated
• Sam ___ (Seuss character)
• Leonard Nimoy's '___ Not Spock'
• 'Don't you know who ___?'
• 'Luke, ___ your father'
• Sam-___
• Sam-__: Seuss character