Changing Show Names?

I am leasing a pony right now, and of course I'd have to ask the owner, but I'd like to change the pony's show name. The pony's owners don't show him and I'm the only one showing him, and I just don't really like his show name.
So how do you change show names?

I don't think you can change registered names?
Usually show name is just the name you enter on the show forms, there's nothing official about it.

Yup. I don't believe you can change the registered name. If you can, you have to be the sole owner, and it's a huge fee.
I would just write a different name on the paper :) Unless you are showing in a circut for points - then your stuck with his name. What is it, if you don't mind me asking?