How to hack MediaWiki to make anonymous users display as Anonymous?

I understand that a wiki already did this but I don't know anything more about it. I took a shot at writing such an extension on a wiki I want to implement this on without any success but I don't know anything about making them so I have no idea if I came close.

I am guessing that the server side code should change the logged name from the IP address to Anonymous.

That's basically it. It logs the editor's IP. I just use an VPN.