The characters, also known as Shimejis, are simple animations which will play around and wander across your screen. Once you install the app, you will get two Shimeji, but you can download more for free by visiting the store page found inside the app. Just send me a note or comment and I'll remove it. If an artist has an issue with me reposting their shimejis with a Mac format, I will happily remove them.
I don't draw the shimejis: I just put them in programs for the mac. I post shimejis that I've reformatted for the mac, so all us Apple-using deviants can get in on the fun with no fuss. To enable this on Mac, click on the Apple logo in the top-left corner, go to 'System Preferences,' then click on 'Universal Access,' and check the box next to 'Enable access for assistive devices'.
You can keep your current wallpaper and add the animated mascots on top. Shimeji is a software customization tool that allows users to add adorable animations as companions on their computer screen.