This was the last acting role for Percy Kilbride. Ma and Pa Kettle at Waikiki (1955), which was filmed several years earlier, was not released until 1955.
The doggy-sweater is shown to be unravelling in a circular motion around the dog's neck, but then the loosening yarn "changes direction" and starts "travelling the other way" along the edge of the knitted fabric, and "magically" becoming re-woven and "adding" itself back onto the edge as it goes instead of being removed; obviously just a reused/reversed section of footage of the yarn unravelling.