If they allowed nudity at that time on NHK I'll tell you that the next Ghibli movie will be directed by Quentin Tarantino.
What I mean is that it's got interesting camera angles. And they focus on weird places. I'm not the only one saying it's at least a little weird for a kid's show, there were some similar comments on some other blogs, like for example this:
http://d.hatena.ne.jp/zgok0079/20050604#p1 or　http://d.hatena.ne.jp/zgok0079/20050521
http://www.accessup.org/anime_j/Zettai%2520Shounen.html
http://blue-cosmos.seesaa.net/category/393522.html
http://xera.dyndns.org/usrbbs/test/write.php?res=1693(imageboard)
And of course, the 2ch official thread here:
http://anime.2ch.net/test/read.cgi/anime/1117453810/
All talking about Zettai shounen being ero in some-way or another...
Of course at it's core the story is a fantasy/sci-fi/coming of age thing, but what's with all the other weird stuff?