BEIJING  Since its first unheralded appearance in January on a Chinese Web page, the grass-mud horse has become nothing less than a phenomenon.

A YouTube children’s song about the beast has drawn nearly 1.4 million viewers. A grass-mud horse cartoon has logged a quarter million more views. A nature documentary on its habits attracted 180,000 more. Stores are selling grass-mud horse dolls. Chinese intellectuals are writing treatises on the grass-mud horse’s social importance. The story of the grass-mud horse’s struggle against the evil river crab has spread far and wide across the Chinese online community.

Not bad for a mythical creature whose name, in Chinese, sounds very much like an especially vile obscenity. Which is precisely the point.

The grass-mud horse is an example of something that, in China’s authoritarian system, passes as subversive behavior. Conceived as an impish protest against censorship, the foul-named little horse has not merely made government censors look ridiculous, although it has surely done that.