Smudge and Cholmondeley used to wear flea collars, and their fur never recovered properly from it. There’s always that phantom line around the neck where the collar used to be. Luckily, Smith is a cartoon cat so all he has to do is shake himself vigorously and his fur will return to normal, in the same way Tom from Tom and Jerry could do when smashed in the face with a saucepan/twisted into a pretzel/grated by a tennis racket/blown up by a bomb, etc.