I always imagined there was a play on prank/plank going on here (think of the way that some East Asians struggle to distinguish between the r and l sounds in English). In the larger context, we are in the midst of Jeoffery's morning ritual. He has just leaped to catch the musk (which I always took to be a scent or perfume, Jeoffry's answer to incense, making the action akin to an act of spiritual cleansing, although even here multiple meanings open up [musk = muskrat?]). He is now rubbing his body against some surface, such as planks of wood, to work the perfume in. The play on prank/plank would also suggest the generally mischievious quality of the action and cats in general, as well as the lesser known usage of prank as a verb meaning to show oneself off. But I'm just speculating.