Nick Lee (@nickplee on Twitter) has squeezed the Mini vMac Emulator on the Apple Watch.
The video below shows the feat, where you can see OS 7 booting and running on the tiny Apple Watch screen.
It is noticeable that it runs slow, and probably there is no real use for that, however it is a incredible achievement, also showing how much the technology evolved over the years!
Source: Call A.P.P.L.E