DISEASE--Dog exercises hard and a. eats large mouthfuls of snow (Winter Blap
Disease) or b. drinks a bucket of water (Summer Blap Disease) Within 2 minutes
of returning inside the dog spews out
GARKS--Dog suddenly clears his throat with loud and dramatic 'gggaark, gggark,' noises, generally followed by prolonged 'iiikssss' and then loud satisfied smacking noises. There is nothing on the rug. Don't investigate, you don't want to know.
RALFS-- Appropos of nothing, the dog strolls into the dining room and waits til the innocent dinner guests are all watching him. Then with a single deep gut-wrenching 'raaaalfff' disgorges the entire week's contents of his stomach on the dining room rug. VARIATION: then he eats it.
In all the above events, the dog is entirely healthy and indeed deeply pleased with himself.