British YouTuber and gamer Harry Brewis (a.k.a Hbomberguy) has raised over $340,000 for Mermaids, a charity that supports transgender children—with the help of support from New York congresswoman Alexandria Ocasio-Cortez, Cher, and Chelsea Manning.

On Friday, Brewis told his YouTube followers that he would embark on the endurance feat of playing Donkey Kong 64 from start to finish in a single go. His aim was to raise money for the charity after it was the subject of a defunding campaign organized through Mumsnet, an internet parenting forum that has become notorious for transphobic posts.

Brewis told viewers in a video: "I chose to support [Mermaids] because as a person living in Britain, I find the media discussion around this issue to be woefully misinformed, and I’d like to do my bit to help support the people who do the hard work of contributing to people’s thinking on an issue."

After tweeting in support of Brewis, Ocasio-Cortez joined his stream as he entered his 50th hour of playing the Nintendo 64 game to a live audience of about 17,000 viewers.

"Trans rights [are] a no brainer. Trans rights are civil rights are human rights," she said, adding, "We mean equal rights for all, no asterisks, no fine print, no nothing."

She also said of the housing and healthcare issues faced by the trans community: "When you have the added layer of discrimination, it makes these issues much more acute in their crises than they usually are on average for other people. It's important that we do talk about these issues in an economic frame, but not let go of the fact that discrimination is a core reason for the economic hardship."

Ocasio-Cortez said that whistleblower Chelsea Manning, who also joined the Twitch stream, had alerted her to its existence. Cher also retweeted the stream.

Brewis hit $340,000 in donations after finishing Donkey Kong in 57 hours. He said that he had the idea to raise money for Mermaids when a £500,000 (approximately $643,700) grant from the Big Lottery Fund, a public body that funds charitable projects, was put at risk after Irish comedy writer Graham Linehan urged Mumsnet users to complain about the funding. Brewis described Linehan in a video as a "piss-boy" who was "very angry about trans people all day nowadays."