Originally, the ceremony used a variety of rodents and mustelids, but over time most people agreed it made sense to standardize on a specific individual ground squirrel in Pennsylvania.
This is funny in a whole different surreal way in the wider context of xkcd, because of the black hat
Without context it could easily be assumed that the character in the black hat was a foreigner who didn’t know about the US custom, or perhaps a visitor from the past, in the vein of “explain this to a Victorian child or a medieval peasant”
But most times when the black-hatted character appears in xkcd, he is simply a villain who messes with people and causes harm for his own amusement
(i.e. a black-hat hacker. Although his “hacks” do include simple physical harm like knocking people off the world’s tallest escalator by installing a chin-up bar at the top, or cutting badly-parked cars in half to fit better into parking spaces)
And as far as I can remember he does seem to have a pretty thorough understanding of United States culture… for him to genuinely need Groundhog Day explained would surprise me a lot
So, to a more seasoned reader of xkcd, it is natural to imagine that he’s pretending to be unaware of it, as a cruel prank of sorts
Perhaps he demands this explanation from the same person every day, as part of an elaborate scheme to convince this person they are indeed stuck in a time loop? I feel that might be quite in character
