If you sit down on a sofa, a cat will often try to find a comfy spot to nestle into, and if needed, attempt to dig into that potential space. Note- never wear a sheep (aka. woolly cardigan/jumper) when sitting on a sofa for a cat will dig and then find a strand of wool to entertain themselves with. But it must be said, they do indeed make mighty fine friendly feet warmers or hot water bottles which is marvelous if you have notoriously chilly feet such as myself.
The ginger Tom cat is my Auntie's. It has a balancing problem so when it sits on your lap it tends to fall off which is quite unfortunate if it wishes to climb onto higher platforms such as fences to catch bees.