When the Spanish king Juan Carlos turned to Hugo Chavez and said to him, a touch irritably, "Why don't you shut up?", little did he know that his breach of diplomatic protocol would become a smash hit across the country.

Were the king to claim image rights over his less-than-diplomatic outburst, he could find himself a nice little earner, as those five famous words have become a multi-million euro business, selling ringtones, mugs, T-shirts and websites.

According to David Bravo, a lawyer specialising in IT law and intellectual property, "the use of the sentence 'why don't you shut up?' in ringtones ... is a violation of his image rights".

An estimated 500,000 people have already downloaded the ringtone, generating around €1.5m (£1m), but many companies have circumvented any potential problems over rights by using an actor's voice instead of the king's.

Over 700 videos have appeared on YouTube, with parodies ranging from a Benny Hill sketch to a Nike advert featuring the Brazilian star Ronaldinho, which ends: "Juan do it. Just shut up."

Meanwhile, the Peña brothers, who run a small T-shirt company, have found themselves overwhelmed with orders for their design inspired by the king. They normally expect to sell 800 T-shirts in a year, but in the week of the king's outburst their orders reached over 1,000.

While Spain and Venezuela might now be trying to smooth over the diplomatic stand-off, it seems the king won't be shutting up anytime soon.