Sounds familiar. My son TJ started talking in sentences when he was a little over a year, and NEVER quit. One day, when he was about 3, I was so frustrated with him, I told him we were going to play a game. I was him and he was me. I started by asking for a cookie, to watch TV, call Seweetie (his grandma), etc.
He looked at me and said, "Why don't you go watch TV, be quiet, go take a nap, shut up for once, NO, Stop that, why did you do that?", well you get the idea. My face was very red. I had a little bit more patience after that.