Counting to five at 9 months... I'm a little impressed

So while on vacation our good friend was tapping with Andy, our 9 month old.  He would tap a few times and the Andy would tap.  After watching them I realized something; Andy was copying him.  He would tap 5 times with his hand, Andy would tap 5 times with his hand.  Then another time Andy copied him using both hands one at a time!

Has anyone else seen this with their babies?  I'm a first time mom so I don't know how normal this is, but like I said, I'm pretty darn proud of my little fella!