If you've ever rocked a band T-shirt, plastered your walls with posters or etched a singer's name into a school desk, you know what it means to be a fan.
If you've ever said the boys of One Direction mean more to you than your family, you should meet Elif, one of four fan girls profiled in I Used To Be Normal: A Boyband Fangirl Story.
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The documentary follows four women, aged 16 - 64, all of whom have given themselves over to the unyielding hysteria that comes with utter boy band adoration.
"The director, Jessica Leski, at the age of 31, fell in love with One Direction," says the film's producer Rita Walsh, who herself identifies as a Backstreet Boy fan girl.
"She should have known better, but she saw Harry Style's cheekbones and that was it."
The movie's opening sequence takes us from black and white footage of hair-pulling Beatlemania to the modern day equivalent: sobbing uncontrollably at a YouTube video of a One Direction concert.
The boy bands might have changed, but being a fan girl is forever.
But what is it about boys in matching denim outfits and teenage girls that makes them a match made in marketing heaven?
"I think it's because they're so beautifully crafted. There's a character - there's one for you, there's one for your friend... you can switch, if you like," says Walsh.
"For teenage girls, who are just developing their sense of adult identity... it's the first thing they can pick for themselves."
Despite admitting to moments of genuine concern for the fan girls, Walsh says their obsessions have helped make them the people they are today, which she calls "amazing".
The film brings its subject's fantasies to life through beautifully animated sequences - sharing a bowl of soup with Niall from 1D, a swimming lesson from Backstreet Boy Nick Carter - but they're not poking fun.
"We really wanted to empower the teenage girl experience - there's a lot of judgement, and people tend to dismiss teenage girls and whatever they love," Walsh says.
"People treat it as transient and stupid, but the girls are having really genuine experiences."
And while the worshipping usually begins in the heady whirlwind that is puberty, Walsh assures me it's okay to still wear your Backstreet Boys shirt to bed in your late 20s - hypothetically, of course.
- I Used To Be Normal: A Boyband Fangirl Story is playing at the 2018 NZ International Film Festival.