According to The Mirror, Styles spent three hours at his pal's bash after turning up at 1.30am - where he was surrounded by starstruck Sheffield students.
The girls took to Twitter to tell of their night with Hazza, with one girl PheAspinwallxxx posting: "He told her she was very attractive and to take off her Minnie Mouse suit lol.”
Another party-goer, named Georgina Dick, tweeted: "We also talked about whether he would have gone to uni and football teams while we washed up together." Bethany Chapman added: “Best day of my life! Chilled with him for like 3 hours!!! I was literally in shock the whole time, trying to play it cool haha, but inside i was freaking out!!!!!”
Despite Harry partying with the girls, a source told the newspaper that it was a purely innocent affair: "He simply dropped by as a favour for a friend and was polite and friendly to everyone he met."
Over the weekend, Styles' pal Nick Grimshawwas quoted as saying that the 18-year old had "fallen for Taylor in a big way", adding: "At first I wasn't sure if the relationship was a real one but I talk to him a lot and it seems to be that she's the one – for now, anyway.
"American artists are usually really, really boring and reserved but Taylor is fun. She's always up for a laugh and is really good company."
He continued: "Harry likes people who make him laugh. I talk to Harry a lot on the phone while he's away touring and he talks about her a lot. He is very happy with her.
"I like her a lot too, she came on my show recently and we had a really fun time."