If you ever stumble across Dudley lying on a couch making this precise expression (which you definitely will; it's only a matter of time), the proper response, just so you know, is to say: "WHO'S SUCH A BOO BOOS?! LORD DUDLINGTON, YOU ARE THE BIGGEST BOO BOO HEAD IN ALL THE LAND!" in a very dramatic deep baby voice, until he rolls onto his back with his legs in the air and makes a very silly face at you with his tongue lolling out.
Then, just to be safe, you should probably give him ALL THE TREATS followed by ALL THE SNUGGLES. All of them!