Ah, I think you're describing the famous back-squirm. Pongo's routine in the morning is to lie at the bottom of the stairs waiting for his dad to come down. Then he throws himself down for: (a) tummy rub; (b) morning facial - massage of cheeks and ears; (c) back squirm; (d) a moment of complete zen stillness - we think he running down his mental checklist of "have I done everything now?"; (e) jump up on all four feet and shake. Right, ready to go round the garden for a pee now. C'mon.