Why does Cristiano Ronaldo have zigzag hair?

Portugal's Cristiano Ronaldo has been trending around the world since late on Sunday, not for his footballing prowess, but his latest haircut - a bold zigzag-y stripe on the right-hand side of his head.

When he first sported the new style in public, a few hours before the Portugal v USA game, Twitter erupted in a collective round of head-scratching and mickey-taking. Some suggested it merited a place among the World Cup's "worst haircuts". Others wondered if it was a funky-looking "7" - similar to Ghana's Asamoah Gyan, who has a yellow "3" dyed into his hair.

And there were thousands of references to a certain wizard's scar. "What's with Ronaldo's hair? Is he sponsored by Harry Potter now or something?" for example.

But the widespread mockery of his locks - admittedly mostly from Americans - soon morphed into something completely different. And it sent the Twitter rumour mill into overdrive. A single tweet from a regular football fan with 900 followers seems to have been the trigger.The tweet read: "Ronaldo cut his hair to match the scar of a young fan who had surgery to remove a brain tumor last week. #respect."

That tweet has now been shared more than 11,000 times. It was also copied word-for-word and reposted by numerous larger accounts. In all, there have been about 50,000 tweets and retweets. The problem is, there's nothing to suggest this is anything but a rumour. Ronaldo himself has not posted to his social media accounts since before Sunday's match, and neither his agent nor the Portugal team have responded to our request for clarification.