Here I present a great panel from issue seven of the UK Masters of the Universe comic. After a skirmish with Skeletor and his Evil Warriors He-Man begins his transformation back into Prince Adam. However, upon summoning the power something strange happens resulting in the appearance of two separate beings. As the animated series was incredibly slow to air all the episodes in the UK, this was one of the earliest times I can recall seeing He-Man transform back into Prince Adam. Even more interesting is the phrase he uses, which in later UK comic stories would be altered from "I Have The Power!" to "I am Adam!" I remember when I was a kid being absolutely awestruck when I turned the page and saw this image!
(click on the image to see it at full-size)