I didn't hear about them in China, but i did hear about some in The US.
That would be funny to have some kind of crypto wrapper, so you think you have a litecoin, but it was filled with Pacoin. Of course it could only be done in art, cause the computer logic would just throw it out... you couldn't do it.
Even with some kind of blockchain that spans blockchains, your computer would tell you exactly what was in the thing you had.