Slugs and snails and puppy dogs' tails

So I'm as comfortably ensconced on the lounge as that rotten loungesuite allows me to be, when the Cherub climbs onto me and says Mummy can you smell my bottom? And he starts waving his rear-end at me. And I say with alarm and distaste in my voice Why? Have you done a stinky fart? and he says Just smell my bottom and I protest vehemently, I don't want to smell your bottom, but by then he's brought the stinky fart over with him so in effect I have smelt his stinky bottom but he won't get off me until I tell him I've smelt his bottom and then he hops off me with a pleased and slightly guilty smile and tells me I smelled it too.