More noteworthy, however, is the fact it was her 27th trip. Avenhouse is a Disney "geek", who plans her trips with military precision. "When we go we take friends and we follow a very specific plan to make sure we ride all the rides and experience everything," she says. "Sure, they might call me the Disney Nazi, but after four days they have done absolutely every single thing that they possibly could."

Her Disney obsession doesn't stop there; her Eastwood home is a shrine to all things Disney. "I collect Maleficent and the Cheshire Cat," she says. "I have probably 4000 pieces of collectibles including posters, original art cels … that sort of thing."

Welcome to the obsessive, every-so-slightly bonkers and very influential world of 21st-century pop-culture geekery, which dominates the lives of millions of people and comes in a thousand different flavours. Think anime geeks, comic-book geeks, sci-fi geeks, gamer geeks, TV-show geeks, fantasy geeks and, yes, Disney geeks.

Each group devolves into a bewildering array of sub-clans from Buffy the Vampire Slayer fans to those who love My Little Pony, from X-Men devotees to Call of Duty aficionados.

Although many geeks don't restrict themselves to a single field of fandom. "It's not just Disney – I have other problems as well, as my husband calls it," says Avenhouse. "I also love Star Wars. And between us, when we got married, there was a collection of 60,000 comic books that got combined."

For those on the outside, both the fans and their passionate devotion to whatever corner of the geek universe moves them can seem bewildering. None of this is helped by the difficulty in actually defining "geek".

Originally the term carried pejorative overtones, with implications of anti-social tendencies and an unhealthy devotion to a narrow sphere of interest. But gradually the word has been reclaimed to the point where now it is worn (mostly) with pride.

Scott Knight is an assistant professor at Bond University who studies contemporary pop culture. "The term has shifted from being a negative descriptor to something that has become a bit of a term of endearment," he says.

As well as having an academic interest in the topic, Knight happily wears the geek label and has a particular passion for the US television series Buffy the Vampire Slayer. The show provides endless possibilities for dissection, discussion and research, making it perfect geek fodder.

"I think this is incredible art work akin to any kind of high art that you can consider that has been produced within the last 30 years. It has the depth and complexity and nuance that brand it as a work of extraordinary intrinsic excellence," he says.

While the geek universe is characterised in part by its diversity, there is one overall linking factor – the explosion of internet technology. Once, if you had a particular interest in, say, Doctor Who, connecting with others who shared your passion might involve subscribing to a fitfully published fanzine or, if you were lucky, attending club meetings. Now, regardless of how niche you interest is, finding others in your "tribe" is only a click away.

Not only has technology brought individual fans together, it has also enabled one of the other key aspects of modern fandom: unlike their parents, who were passive consumers of books, movies and television shows, Gen Y fans expect to be much more heavily involved with the objects of their interest. They have moved from the margins much closer to the creative centre with blogs, YouTube channels, fan fiction and more.

Academics call it "participatory culture", and Hollywood, in particular, is sitting up and taking notice. "There is a sense that the fans have power and the studios must respect that now," says Knight. "The whole system of entertainment media has shifted in the past decade. If the studios are not inclusive then they are going to die."

Even more, says Knight, it is the fans themselves who are now in charge of making the films and TV series that feed the geek culture mill.

"The fans are now the producers," he says. "Most people would consider the geek god of all geek gods to be Joss Whedon. He is now at the centre of the biggest, current popular franchise in the world – The Avengers. Not only are the fans no longer marginalised but they are the producers of multi-billion dollar franchises."

Perhaps the most obvious manifestation of the new influence wielded by the fans is the annual Comic-Con convention in San Diego, a four-day extravaganza devoted to movies, TV, comic books and gaming that this year drew some 125,000 fans as well as many of Hollywood's biggest names, from both sides of the camera.

"The studios take it incredibly seriously," says Knight. "They build their entire campaigns around Comic-Con and they make sure everyone stops shooting to take the stars to Comic-Con. They know the response they get there will shape not only this film but their whole franchises."

Australia has its own version of Comic-Con. The brainchild of Avenhouse, Oz Comic-Con is now in its third year and will be staged for the first time in Sydney and Brisbane. She expects 30,000 to 40,000 fans to attend in Sydney, attracted by a guest roster that includes the actors William Shatner, Percy Daggs and Orlando Bloom.

"You just revel in what you love," says Avenhouse. "You shop, you meet the fans, you hang out, you watch things, you enjoy the panels, you dress up in your favourite costume or you just wear the T-shirt from your favourite TV show or movie or comic. You're just at one with your people."

Just like at the US event, the geek masses will expect to get up close and personal with the objects of their passions. Perhaps surprisingly, this is a two-way street. "Most of the guests love the Q and A sessions, where they get to sit down and talk and share their experiences and answer fans' questions," says Avenhouse. "When we had Benedict Cumberbatch out, he said one of the absolute highlights for him was to have this moment to sit there and talk to the fans."

So, where does it all start? Are geeks born or made? It appears it is a little bit of both, with early childhood influences an important factor. Chloe ("but I go by the name 'Feisty Cuffs'") Lyttle's particular passion is cosplay – making and wearing the costumes of heroes such as Poison Ivy, Princess Mononoke and My Little Pony.

"I guess I was always into comics and video games and anime when I was growing up and then I joined the local university anime club," she says. "They used to do lots of screenings and fun events. I made my first costume and attended a convention and haven't looked back since."

For Avenhouse, it was the influence of an older brother. "I was raised on Tolkien, Star Wars, Star Trek ... all the good stuff," she says. "It sort of grew from there."

It's tempting to dismiss all this collecting, dissecting, dressing-up and obsessing as so much childish nonsense from an over-indulged generation that refuses to join the "adult" world and has way too much money and time. But behind all the colour and movement there is something deeper at work, involving a need as old as humanity – to be part of a tribe or a community. To belong.

"When you go to a convention you can make eye contact with someone and instantly you know they are a fan and you're obviously a fan of whatever costume you are wearing," says Lyttle. "You have this instant connection with people and it's great to be able to geek out together."

Avenhouse agrees. "Most of my friends I have met because of what we love," she says. "I've had some amazing friends for 20 years because we were two 17-year-old girls at a Star Wars convention. It's a wonderful thing."

In Lyttle's world that connection and sense of being part of a supportive community extends online. "My experience in the cosplay community is that everyone has been really embracing," she says. "I contact people who you would call 'cosfamous' about how they made a certain costume and they have all been really forthcoming and really helpful. It's really encouraging. There aren't many hobbies where there is so much nurturing of people's talent."

Avenhouse, who is 36, can never see a point for her personally where the geeky flame will die.

"Some people love sport," she says. "Some people love gardening or reading. Some people like to travel. Everybody has a passion, something that they dedicate their spare time to. For some people it's just geek culture."

Oz Comic-Con Sydney is at the Exhibition Centre @ Glebe Island on September 13 and 14.