Possible Clues:

• 'Isn't that somethin'?'
• "Hmm, I didn't know that!"
• Head-scratcher's comment
• "Aw" go-with
• "Really!"
• ''Wow!'' to Beaver Cleaver
• 'Oh wow!'
• "My goodness"
• Word said while scratching the head
• 'Hmm, I don't know about that'