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'Iconic': Harry Styles and Millie Bobby Brown hung out at an Ariana Grande concert

Hannah Yasharoff

Ariana Grande took her Sweetener tour to London this weekend, where two VIP guests caught fans' attentions.

Singer Harry Styles and "Stranger Things" star Millie Bobby Brown were spotted living it up at the concert, and fans on social media couldn't get enough of it. 

"Did someone say (expletive) iconic?" Twitter user @nervousrem marveled at the idea of Brown, Styles and Grande together in the same room. 

Cellphone videos shot by the audience capture Styles, 25, and Brown, 15, chatting and laughing during Grande's show. Styles was recorded giving fans high fives as he entered the arena, wearing a white T-shirt and bell-bottoms. 

On Sunday, Brown shared a group photo from The 02 Arena with the caption "enola holmes crew." She's slated to star in a movie about Sherlock Holmes' younger sister, also featuring Henry Cavill and Helena Bonham Carter. 

One Direction alum Styles was seen dancing and singing along to Grande's lyrics, much to the delight of pop fans.

"Harry seriously raised his glass and screamed 'something about you makes me feel like a dangerous woman,' " @ftdtonvinyl tweeted with a video of Styles singing along to Grande's "Dangerous Woman." 

Other fangirled over Styles on behalf of Brown.

"never wanted to be millie bobby brown so bad in my life," @peacefulstark tweeted. 

'IMAGINE BEING MILLIE BOBBY BROWN. WATCHING ARIANA GRANDE WHILST STANDING WITH HARRY STYLES," @grandesgiaw tweeted

"the most ambitious crossover event in history," @m_ollymac joked. 

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This article originally appeared on USA TODAY: Ariana Grande fans freak at Harry Styles, Millie Bobby Brown chatting