After I know someone well enough, I usually end up giving them nicknames that I call them... pretty much anything other than their real name. They may or may not actually like the nickname, and it may randomly change over time. I have one friend who may literally have a hundred or so nicknames depending on which one I remember at the time. Mostly, I do it because I find the nicknames hilarious. Same goes for animals... they get dozens of nicknames.
Are you a nicknamer?