Developer Nick Lee has shared a video showing off the nearly two decades old Macintosh OS, System 7.5.5 running on an Apple Watch running watchOS2. System 7.5.5 was released on September 27,1996.
![Developer Runs Macintosh OS, System 7.5.5 on Apple Watch Running watchOS 2.0 Developer Runs Macintosh OS, System 7.5.5 on Apple Watch Running watchOS 2.0](http://www.mactrast.com/wp-content/uploads/2015/06/Developer_Runs_Macintosh_OS__System_7_5_5_on_Apple_Watch_Running_watchOS_2_0.jpg)
Lee hacked the Apple Watch to run Macintosh OS via the Mini vMac Macintosh Emulator, which was designed to allow users of newer computers to run software designed for early Macintosh computers. Macintosh OS, System 7.5.5 was designed to run on a PowerPC Mac.
(Via MacRumors)