Lots of cats sleep on dogs.
Dogs make good pillows.
https://static.boredpanda.com/blog/wp-content/uploads/2015/02/cute-cats-sleeping-on-dogs-6__605.jpg
http://earthporm.com/wp-content/uploads/2015/03/cute-cats-sleeping-on-dogs-4__605.jpg
https://static.boredpanda.com/blog/wp-content/uploads/2015/02/cute-cats-sleeping-on-dogs-20__605.jpg
Lots of cats sleep on dogs.
Dogs make good pillows.
https://static.boredpanda.com/blog/wp-content/uploads/2015/02/cute-cats-sleeping-on-dogs-6__605.jpg
http://earthporm.com/wp-content/uploads/2015/03/cute-cats-sleeping-on-dogs-4__605.jpg
https://static.boredpanda.com/blog/wp-content/uploads/2015/02/cute-cats-sleeping-on-dogs-20__605.jpg