The cats are to be worked top-down in the round using magic loop. They are quite small (even worsted weight cats) and fit in the palm of your hand. These cats can be made with any yarn at any gauge, as long as the needles are small enough that the stuffing won’t show through. I like to use leftover sock yarn. I don’t recommend slippery yarn or yarn that splits easily, especially at the smaller gauges. Knit cats and sleeping bags at the same gauge so they will fit snugly. Use black stuffing for darker cats, if you can find it. You could also experiment with weighted pellets.