I love buying him things that are very loud or something I know a parent would hate because I know he'll take it home to his mom's.
He has a very interesting word choice. I don't know if his mom taught him to use labels. He calls me Aunt April. And my grandpa where my sister 2 kids just calls him grandpa he will call him great-grandpa. Sometimes I use the uncle or aunt title, but not common. Just wasn't raised that way.