They are how potentially millions of people see us every day. They are a snapshot of us that we are happy to share. A window into our souls, even. They are what, in some people's eyes anyway, define us.
They are our avatars or online profile pictures.
Choosing an avatar, can be a complex business. You need something that shows a little of the real you, without giving too much away. It is, after all, how you will be judged.
The good ones are memorable - you can instantly recognise them in your timelines, and you are drawn to them.
The bad ones are just ripe for mockery, and duly receive it in many cases.
But here, at tweetyouravi.tumblr.com we have something very different. We have mimicry, but it seems it's out of admiration, or even adoration.
Some of the top tweeters have had their avatars lampooned by followers, and the results are brilliant.
If you have a few favourites, you can add to this growing list. And it seems that most of the subjects quite like the attention. What is it they say about imitation being the sincerest form of flattery...?