What would happen if you were to gather a mole of moles in one place?
The outer surface of the Mole planet radiates heat into space and freezes. Because the moles form a literal fur coat, when frozen it insulates the interior of the planet and slows the loss of heat to space. However, the flow of heat in the liquid interior is dominated by convection. Plumes of hot meat and bubbles of trapped gases like methane -- along with the air from the lungs of the deceased moles -- periodically rise through the mole crust and erupt volcanically from the surface, a geyser of death blasting mole bodies free of the planet.
XKCD doesn't usually do it for me, but his new "What If?" series is off to a decent start. Relativistic Baseball is also nicely gory.