Not something you see that often, in fact this is probably the first time it has been accomplished. According to an article over on engadget, Toni Nikkanen of Finland has managed to hack Mac OS X onto the Nokia N900.
This is believed to be the first time Mac OS X has been ported to a mobile phone, and we have a video of the occasion for your viewing pleasure below which lasts bang on six minutes.
Niikkanen uses PearPC which is a PowerPC emulator to accomplish his hack to get OS X 1.3 Panther onto the Nokia N900. However it does appear to be somewhat sluggish, probably too sluggish to be of any real use.
Apparently it take a staggering 90 minutes to boot and the cursor moves at a snails pace, but hit up the video below and check it out to see what you think.