Wow, the guys from Always Innovating are amazing! They managed to run 4 operating systems at once on a Beagle Board (and on the Touch Book and Smart Book tablets): Android, Ubuntu, Chrome OS and AIOS. By pressing the User Button on the Beagle Board you can switch between the started OS-es. Why would you need that? I have no idea, but I find it cool!
https://www.youtube.com/watch?v=yseT4USH8SY