In Drew Barrymore's film Never Beed Kissed there is a girl in the background wearing She-Ra's crown.
Its in the fancy dress bit, almost at the end of the film. She is giving a speach about how the cool kids really wearn't all that cool and the neards were infact were the coolest people she knew. She had just been crowned prome queen and the dog food was about to be thrown at her friend.
A new line MOTU poster made in into an episode of the British sitcom Shameless last week. It was in a scene near the end of the episode. It was when the little boy called Liem, was in his room. You would have to look to see it, but it was there. There's a close up where you can see it clearly. Mostly the Logo.
There always used to be a He-Man quilt shown on episodes of the Irish Comedy Father Ted, (Classic) Almost every episode. for sure.
Finally, there was a scene in the first British Big Brother series when a crazy contestent called Nicky had covered herself in body paint. She held aloft a make beleve sword and shouted quite seriously "By The Power Of Grayskull!" It was shown in her best bits (I think). This was years ago though!