"Lap warmers" refers to objects or devices that are used to keep one's lap warm, often during colder weather. They provide warmth and comfort by resting on the lap and generating heat. Full definition
This little guy is the happiest little lap warmer ever. (marleysmutts.org)
They still possess all core traits of a «lap warming dog» including their reduced size, their calm and friendly personality and their craving for love and attention. (wtfrenchie.com)