Possible Clues:

• '___ Dead?' (Mark Twain play)
• "__ kidding?"
• "Who __ kidding?"
• '__ kidding?'
• “___ Dead?” (Mark Twain play)
• 'This --' (phone phrase)
• '___ not jealous?': Emilia to Desdemona
• "__ serious?"
• '___ for real?' ('Can you believe that guy?')
• ''Who __ kidding?''