What's in a name?

My archives professor has called me Ms. Gray, Rebecca, Becky, and Andy. He seems to think this is funny. He will call other students Ms. [insert last name here], and one girl he calls "Sarah with an H," but I don't believe he's called anyone else by their middle name. And I don't recall his ever actually calling me Andi. He tried tonight, but it came out as Andy, and I didn't feel like correcting him. I guess I don't mind though. It's more amusing than anything.