While the antipodes of China include Argentina with its Atucha Nuclear Power Plant the phrasing is metaphorical; there is no way a core could penetrate the several-kilometer thickness of the Earth’s crust, and even if it did melt to the center of the Earth, it would not travel back upwards against the pull of gravity. Moreover, any tunnel behind the material would be closed by immense lithostatic pressure.
You need to explain that “China” part in there for me. I understand the Stockholm part of the joke, but not the other one.
Thanks xkcd! Wait, it’s wikipedia???