how do you do?

Benjamin repeats everything I say. He repeats prayers pretty well except sometimes he won't start repeating until I say the magic words ,"thank you for grandma and papa" then he'll say, "papa!" enthusiastically. Coming after a child who couldn't be bribed to say anything on command, he is quite the little orator. His vocabulary is pretty limited to single words and he has yet to string several words together on his own. But the other day while watching The Wiggles (of course), I heard Sam Wiggle say, "How do you do?" And right after that I heard Benjamin say very clearly, "How do you do? " It was one of the funniest things he's done. Now he will just randomly ask ,"how do you do?" when he wants to make me laugh.