Possible Clues:

• "You're not the only one!"
• 'You're not the only one!'
• Retort from someone who refuses to be outdone
• 'Me, too!'
• Assertion from one who won't be outdone
• Copycat's comment
• "Me too!"
• Confident comeback
• Boaster's reply to a boast
• Retort from one who won't be one-upped