Chuck Norris' calendar goes directly from March 31st to April 2nd. Nobody fools Chuck Norris.

• Martin Wainwright details some of history's best April Fools jokes in The Guardian.

"The Financial Times was always doing special reports on little countries I'd never heard of," says former Guardian advertising rep Philip Davies. "I was thinking about April Fool's Day 1977 and I thought, why don't we just make a country up?" Special reports editor Stuart St Clair Legge suggested the title that was to become a legend: San Serriffe, part typographic pun, part credible name for a tropical isle.

It also had the special appropriateness for the Guardian of challenging spelling. During its long relationship with San Serriffe, starting with the original supplement itself, the paper has printed the name with carefree inconsistency, using every possible variation of "r"s and "f"s, and, on one occasion, two "e"s.

Picking up Legge's theme, staffer Geoffrey Taylor designed a shrunken semicolon-shaped version of New Zealand's twin islands and based everything on the rich vocabulary of print. Leading islanders, such as the dictator General Pica, and places like the capital, Bodoni, were named after fonts of type and their measurements: he even got away with a wilderness area on the north island called Wodj of Type.

The islands were positioned off the Canaries and with just over three days to go, the final shape of the major, seven-broadsheet-page supplement was drawn up. Then, in the late afternoon of March 27, two jumbo jets collided at Tenerife airport, causing the worst aviation disaster in the world, in which 583 people died. The delicate web of April Fool fantasy suddenly seemed marginal. The editor, Peter Preston, teetered on the edge of pulling San Serriffe, but fortunately it was not abandoned. With a Herculean effort, the islands were relocated in the Indian Ocean, their history, flora and fauna completely revised.

So San Serriffe indelibly joined the map of the world. Next morning, the phone calls started early, the letters followed later. Thousands of readers were taken in; spin-offs soon included "I've been to San Serriffe" car stickers and a T-shirt from the islands, which sold a record 12,000 to readers.