Mine, I had done for my birthday, last year. The big 20. w00p.

It's a band, with Calvin and Hobbes dancing in a circle around my arm. In their pyjamas, no less.

As for why I got it? Well, my middle name is Calvin, that's a good start. I love the cartoon, that's another reason. But mostly, I had it done to remind me to keep dreaming, keep laughing, and to reinforce that the best part of growing up is the fact that you don't have to.