Throughout Britain parents are receiving letters from real doctors warning them that their apparently healthy children are hiding huge folds of fat in their clothes, and are liable to explode from sheer fatness at any given moment. Apparently children have become so good at concealing their fatness by not being fat that they often don't even weigh very much; a trick they are thought to have learned from balloons.

"It's an epidemic," said Doctor Dick Stunts, from the Skopje Institute for the Study of Sneaky Fat Kids in the Former Yugoslav Republic of Macedonia. "Thin, well proportioned, lightweight fat kids are everywhere. Take a look at this picture of a seemingly normal young girl riding a bike. On the surface she's not overweight, is she? Don't be fooled my friend. She's a crafty, fat heifer.

"I first started to study this problem when I was at university. I noticed a strange phenomenon amongst some of the girls I met there. Late in the evening at some of the local nightclubs they would appear to be svelte young objects of well proportioned loveliness. Much to my horror however I discovered that by the morning they were massive, wobbly, mounds of flesh - much like pigs wearing lipstick. In fact all sorts of things became apparent in broad daylight, including in one rather disturbing case, a large pair of hairy testicles."

The Mayor of London, Boris Johnson, has also joined in the battle against well hidden flab by hailing parents who encourage their children to ride bicycles as heroes. "Everyone should ride a bike everywhere, all the time," he told Stinky Ponky. "I love bikes, me. In fact I married one. Here she is; my beautiful Janine. Isn't she smashing? Check out the handle bars on that. I once went to Amsterdam you know and it was amazing. I spent the entire week riding and riding and riding. I love bikes, did I say that? OOOOOO bikes."

Parent of an accused fat child Dave Watt explained why he found the letter he received so offensive. "It's the way that they say it as much as what they say," he said. "We received a letter about little Johnny yesterday. It says 'Dear Shit Parent, Your child has been measured against some statistics we found in a drawer and we are sorry to tell you that he's a fat little bastard. 

"He'll be dead by Wednesday. Love, the NHS."