My cat has this tattoo in his ear. It doesn't keep him away from my keyboard, but it does seem curiously appropriate.

The practice of placing an identifying tattoo in a cat's ear seems a bizarre practice to me. Permanent, yes, and I suppose the spca would check the animal's ears before doing anything drastic, yet I find it likely that a family who found a cat without other identification might just keep the cat and never notice the tattoo for years after, since a cat's ear is obscured both by fur and by most cats' aversion to having their ears touched. I think it must just be to make male cats who've been neutered feel better. "I may be a eunuch, but damnit, I'm tough! Check out my tattoo!"