The central character, Nobby, is a middle-aged man who suffers from chronic hemorrhoids. Some people have defended Viz from its critics by pointing out that it is far more sophisticated and subtle in its satire on society and current affairs than one might think; but Nobby's Piles is very much a strip that is unapologetically the sort of silly schoolboy humour that earned Viz the controversy it has attracted in its quarter-of-a-century existence.
In each episode, Nobby endures repeated abuse to his bottom by a series of terrible accidents that only serve to agonize his poor, hemorrhoid-afflicted anus. He has been impaled on a church spire after a parachute jump, had his hemorrhoids stabbed by the rock pick of a mountain climber, fallen into a skip full of broken glass (bottom first of course), and slid down the rusty metal bannister of a flight of steps after an ill-advised skateboard trick went wrong. Much of the pleasure of the strip comes from the anticipation created by the increasingly contrived ways in which these incidents are set up: a typical example might see Nobby's wife trying to apply some hemorrhoid ointment to her husband whilst in a darkened caravan, and show her trying to distinguish between two otherwise identical bottles, one labelled 'Pile Ointment', the other 'Devil's Brand Hell-Fire Jalapeno Sauce - Bang! Bang! Molto Explosivo!' - with a predictable lack of success. Similar to a Tom and Jerry cartoon, Nobby's agonies often cause him to shoot high into the air whilst screaming hideously.
Obviously, the name of the cartoon strip is a play on words, referring to a rhyming slang term for hemorrhoids i.e. Nobbys.