Shimeji-ee:

Shimeji-ee is a Windows desktop mascot that freely wanders and plays around the screen. 
Shimeji Downloads:
 
If these don't work on your computer make sure you have the latest version of Java.

 

Desktop Ponies:

The ponies My Little Pony Friendship is Magic will walk around your screen acting out scenes from the series.

eSheep 64bit scmpoo.png

scmpoo.exe was the original eSheep from Windows 3.1. This is a 64bit remake

Neko

Neko has been around since the dawn of time! Its a cat that chases the mouse, and has customizable skins and behavior.