The Super Mario Bros. Android live wallpaper serves no purpose other than looking cool. Sure, it will probably eat your battery life quicker than you can say "but our princess is another castle" but it's worth it for the attention you'll get when you whip your phone out in front of your pals.
This live wallpaper works on devices with Android 2.1 or higher and you can still add your widgets to the action.
It's not playable, by you at least. Mario is controlled by AI and the levels are randomly generated, so it's not just a video in the background. It's a bit like watching your device play Mario itself.
There are three visual themes for the levels, and it all looks a bit Super Mario Bros. 3 on the NES inspired to us.
You can get the wallpaper from here. Do it, and be the coolest kid in town. At least amongst people with a regard for 8-bit Italian plumbers.