Ever thought you'd see Windows RT on a smartphone? How about a three year old device that's only running a single core and 576MB of ram? Neither did we, so that's why we're so excited to see Windows RT on the HTC HD2. For right now, we only have pictures, so there is a possibility that it's a hoax, but given the source, we doubt it is.
CotullaCode released a collection of pictures of the device via Twitter. Ubuntu, Windows Phone, MeeGo, and basically every Android release has been hacked onto the hardware at one point or another, so it's not so surprising that Windows RT has joined the ranks.
More surprising is the hardware: a 1GHz single-core CPU and 576MB of RAM. I'd keep a bit of skepticism until video proof is released, but it certainly opens the prospects of Windows RT of smartphones, which is something I think most people would go for.