The one thing I've learned is this: you know you've gone from innocent child to cynical adult the day this line from the opening titles stops sounding cool and starts sounding hysterically funny:
"Fabulous secret powers were revealed to me the day I held aloft my magic sword."
It's not that kids aren't dirty-minded -- I learned words from my classmates that some of their parents wouldn't have dreamed of using -- but kids don't look for dirty double meanings in everything. Adults do.
Other bit I noticed: Every episode of "He-Man" ended with a character addressing the audience with some public service announcement, so the producers of the show could prove that they were really setting a good example for kids. I skipped to one of the public service announcements, and it had He-Man lecturing kids on the importance of safety. He finished: "So whether you're riding a bike or driving a car, always put safety first."
Then he rides off on the back of a giant green cat.
That had to be an intentional joke.