A man who was “fat-shamed” on social media when pictures of him dancing were posted online has partied with celebrities in Los Angeles.

Sean O’Brien received support from around the world in March when online trolls captioned a photo of him: “Spotted this specimen trying to dance the other week. He stopped when he saw us laughing.”

But the Liverpudlian became an unlikely celebrity when a social media campaign to track him down was launched.

And now he has appeared on the television dancing with pop star Meghan Trainor before partying with the stars.

He was joined by around 1,000 supporters, including rocker Andrew WK, rapper Pharrell Williams via video, and White House intern-turned-anti-bullying campaigner Monica Lewinsky. Moby, who had previously offered his services for free, was the DJ for the party at the Avalon nightclub.

O’Brien also threw the symbolic first pitch at a baseball game between the Los Angeles Dodgers and the San Diego Padres, wearing a Dodgers shirt with “Dancing Man” on the back.

Sean O'Brien
(Mark J Terrill/AP)

He told Good Morning Britain: “(It was) daunting at first. (I was) a bit worried about how it all happened but it’s turned into the most wonderful journey, I’ve met some of the most wonderful people you can imagine. It’s been truly life-changing.”

When pictures of O’Brien dancing happily before looking downcast were shared online, it first prompted a wave of abuse, but then led to a mass outpouring of support from Twitter users around the world.

A group of American supporters, including writer Cassandra Fairbanks, arranged for him to fly to California for this weekend’s events. The party at Avalon raised money for anti-bullying charities.

Andrew WK told the crowd: “Probably one of the worst things that ever happened to Sean – or that I can imagine happening to anybody – has turned out to probably be one of the best things that has ever happened to him.”

Sean told Good Morning Britain that he was sure he would be fat-shamed in the future, but added: “I’ve always had confidence anyway, I’ve always wanted to dance. It’s just people will pick on you sometimes.

“But what it has taught me is just totally ignore them rather than just blanking them.”