Usernames on CodePen allow uppercase and lowercase. For example, a combination of upper and lower case, like:

http://codepen.io/SaraSoueidan/

You know what was wicked annoying? If you went to, for example:

http://codepen.io/sarasoueidan/

It would fail (404).

Now, it won't. Even if you go to:

http://codepen.io/SarAsOUeiDaN/

You'll get redirected to the correct URL.

HoT DigGiTY doG!