The genderswap thing is pretty old, but it suddenly gained popularity between the elevens after a video that was posted on nicovideo/moontube. It featured the genderswapped versions of the Character CD covers.
The elevens shat bricks and began doing original content (same goes for koreans, chinese and westerners, but most of the original content comes from japan).
There are some videos which even feature full scenes of the anime dubbed by amateurs which actually look pretty good. No fansub has tried to sub them yet.