This meme is sweeping China right now, and as obscene as it is, it’s actually a hilarious protest against censorship (a euphemism for which is ‘harmony’ – which sounds a lot like ‘river crabs’ in Chinese).
If you can’t see the subtitles on this video, here is a text translation (cache linked, since the original was predictably censored).
Here’s a rap take-off:
I have yet to find a translation for this one, but I believe there is an attempt now in the comments.
Grass Mud Horse is just one of 10 Baidu Mythical Creatures that are reportedly taking the Chinese internet by storm.