One of the best parts about this is that you can always download new Shimejis. You can tell it to cycle through its actions, remove it, or add a friend for it to play with. You can right-click on the Shimeji at any time to tell it what to do. It will occasionally sit down and watch you as you work or climb up the side of your screen to hang out near the top. It'll wander around and entertain itself. As soon as you do that, a little Shimeji will drop onto your screen. Shimeji-ee is incredibly easy to install. Well, there's a great program that aims to capture the feeling of those programs - Shimeji-ee.
However, it can't be denied that they brought a touch of personality to your computer and many people sorely miss the days when there were a ton of different assistants to choose from. They took up space on your desktop and gave useless advice and were often in the way far more than they helped. Desktop assistants, by all standards, were horribly designed.