Possible Clues:

• 'r u 4 real?'
• "r u 4 real?"
• "4 real?"
• "rly?"
• 'R u for real?'
• Possible 'OMG!' follow-up
• 'Are you kidding me?,' in texts
• "wait, wut??"
• "r u for real?"
• 'r u kidding me?!'