After Leonardo DiCaprio snipped off his and Harry Styles — owner of some of the most enviable strands in the biz — donated his to charity, we thought we had passed the man-bun mania. Well, it's back, and this time it comes in the form of Matt Damon. Yesterday, the actor debuted his new low bun during a press conference in Beijing, and the internet promptly took notice — mostly because it seemed to have appeared out of thin air. As many pointed out, the 45-year-old was spotted with a close crop of gray-flecked hair less than a month ago. How, then, has a full mane, long enough to be pulled into an updo, suddenly popped up on the star's head? Two theories: He's on some crazy-effective diet that has helped him beat every hair-growth record, ever. Or, the more probable reason: extensions. Damon had a ponytail just last summer — which prompted the internet to go wild and even inspired its own Twitter account. In an interview on The Graham Norton Show, he revealed that his new look, which was for his role in the controversial The Great Wall, was the result of synthetic strands. “There were 700 hair extensions. It was a full day to put them in. They flew somebody all the way to Beijing to put them in," he said on the show. "Then, I had to manage that hair. I have a whole new appreciation for my wife and daughter." The actor hasn't come forward to reveal the meaning behind his return to long hair just yet — but we can certainly guess. Is it for a new role? Is he channeling his The Great Wall character while in China? Identity crisis of some sort? When Damon's ponytail-dedicated account got word of his new style, it tweeted two simple words of enthusiasm: "I'm baaaaack!" Our feelings on the matter? Still up for discussion.