Harry Potter star Tom Felton has told Newsbeat there's a snobbery about some types of superfans.
The actor, who played Draco Malfoy, has been filming a BBC Three documentary about book, film and TV conventions.
He came up with the idea after showing friends a video he filmed at an event a few years ago.
"People were dressed up as Stormtroopers, Gandalf and Dumbledore and my mates thought it was fascinating but also really weird," he says.
"Yet my friends were more than happy to dress up in a football kit and scream at the TV for Manchester United, even though they've never even been to Manchester.
"Why is kicking a ball into a net any less weird than liking a fictitious wizard?
"For things like sport or music, it's considered cool to be a superfan but as soon as it goes into Star Trek or My Little Pony or something a little bit obscure, it becomes a bit weird and people are keen to look down on it."
The documentary features Brian, an infamous New York autograph hunter.
"He would spend all night waiting outside stage doors for the same celebrities," says Tom.
"He has 250 pictures with Daniel Radcliffe and I kept thinking, 'Surely one was enough,' but it's all part of becoming friendly with Daniel and having a community of people with it.
"It's a passion and it gives them something to cheer for. It lets them surround themselves with like-minded people and then give them something to enjoy."
The 27-year-old thinks being a fan can also lift people out of darks times or help them through the death of a loved one.
Every year thousands of fanatics get into elaborate costumes at events like the Wizard World festival in America and Birmingham's Comic Con event, where Felton filmed.
It's a chance for them to meet other fans as well as some of the stars of their favourite shows.
"I wanted to find out what separates the passionate from the obsessive... people who wait outside hotel rooms and [who are] really into a certain project or music or whatever it is," he tells Newsbeat.
He says he's also spoken to Harry Potter star Daniel Radcliffe about superfans in the past.
"When you see fans at premieres usually it's the same faces but you only see them for 10 seconds at a time.
"[But] they start to build up a relationship of support and recognition with the stars - it's hugely rewarding."
Tom Felton Meets the Superfans is on BBC Three on Monday at 21:00 GMT.
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