In Season 2, "Last Call", Reggie and JD (her dog) slide on the hallway floor (a la Tom Cruise from Risky Business). JD slides into the wall and as he gets up and turns, he is clearly missing a sock on his right front paw. (He was wearing the socks to help him slide).

HOWEVER: When the nosey neighbour comes knocking at the Kitchen door, Reggie answers it and JD strolls in.....wearing FOUR socks. (He must be pretty smart to figure out how to put it on).