Answer: iamtoo

AnswerCrossword Clue
IAMTOO"You are not!" comeback
IAMTOO".. old for this"
IAMTOO"You are not!" rejoinder
IAMTOOWords of agreement
IAMTOOPlayground reply to "You are not!"
IAMTOOPlayground retort
IAMTOO"You are not!" retort
IAMTOO"You are not!" response
IAMTOO"Same here!"