Where do they learn this stuff!?

The other day we were at the grocery store. I was pushing Caden forward in the cart at the checkout...he was sitting in the back, and stood up. What happened next floored me, made me giggle, and cry all at the same time.

Caden: Hello!
Clerk: Well, Hello!
Caden: My name is Caden James ****....Nice to meet you! (He then proceeds to put out his hand to shake hers!)

Seriously! Where do they learn this stuff. It was just so dang cute! It also made me realize how fast this little boy is growing up! SIGH!