In his post about development of Windows 8 for ARM processors, Windows president, Steven Sinofsky shared images of Windows 8 running on a phone. Sinofsky says that they did not hav ARM powered tablets in those days so ARM powered phones became the best choice.
Sinofsky added a note saying that the images were just testing and did not hint at new product. Rumors about running Windows 8 on phones have been doing rounds and these early-day trials could be the reason. As Long Zheng pointed out on his blog, these images are from 2010. Windows 8 on ARM powered phones:
PS: The first image reads Windows 7 but if looked at closely it is build 7652 which is widely considered to be one of the early Windows 8 builds.