Here is a striking illustration from the Masters of the Universe Golden Book "Time Trouble" by Luis Eduardo Barreto featuring Prince Adam and Cringer transforming into their other selves! I love the way in which Cringer is illustrated to look like the Filmation character model, but with a lot more expression and freedom in his pose. And Prince Adam's strong pose as he calls upon the power of Castle Grayskull is very impressive. When the Golden Book stories were turned into limited animation videos by the same company, this scene was often used to show the transformation taking place!
(click on the image to see it at full-size)