Rixter: Don't you remember the naked Goku in early Dragon Ball :b?
Yeah, but he's not the only guy to ever draw it that way. I really don't want to make a long post about little boy's penises, but suffice to say that's not his style.
The "Harry Potter ninja manga" was Murasme-kun, which got cancelled pretty early. The author is Mikio Itoh, one of Oda's old co-assistant buddies and the guy who'd appear on wanted posters a lot in the beginning of the series.