As the biggest pop culture convention on the planet, attracting 130,000 attendees over four days to the southern Californian city, this mega-event is notoriously overwhelming. I've spent the morning strolling vast distances between panels, before queuing to get into each one.

Lining up is the signature act of Comic-Con. You line up for panels, for food, for toilets, and to collect tickets so you can line up again to enter a special event later on. For the massive Hall H, where the biggest Hollywood and television stars turn out, people queue through the night.

Now I'm squeezing my way past the hordes shuffling through the cavernous Exhibit Hall, where traders sell every item imaginable.

Then I see him – an Asian-American guy dressed as Wonder Woman. It's the full Amazonian get-up: tiara, metal armbands, blue star-spangled briefs, red and white boots, and a metal plate in the shape of a W hanging over his chest.  I ask if I can take a photo, and he stands smiling, proud and happy in his unconventional attire.

I think to myself that it must take supreme confidence to wear an outfit like that; but as the afternoon wears on and I see the costumes other attendees are wearing, it seems perfectly in keeping with the convention.

Cosplay – dressing up in costume – is a huge and colourful part of Comic-Con, and people don't feel confined to choose characters that match their gender or ethnic background. There are women dressed as the hero Green Arrow and men dressed as Rey from the Star Wars movies, and no one questions their choices.

On top of the variety of costumes is the variety of people. This huge crowd is America at its most diverse and its most co-operative: with every ethnicity present in large numbers, and everyone happily getting along despite the crush. It's a great mix of ages, sizes and shapes, with everyone fitting in.

That's what Comic-Con is really about, I realise: celebrating diversity. In a nation still troubled by racial tensions and economic disadvantage, the happy melange is exhilarating.

If you can get a ticket to Comic-Con via the online lottery staged earlier in the year, it becomes an unforgettable part of a stay in the US.

I flit between panels that vary from sober assessments of the comic book industry to lighthearted tributes to popular TV and film.

One panel simply entitled "1986" is a debate about which was the best movie  30 years ago. For an hour, panellists put up spirited arguments for the likes of Aliens, Highlander, Top Gun, Blue Velvet and Ferris Bueller's Day Off (personally, I have a soft spot for Labyrinth with David Bowie).

A more serious panel brings together academics to discuss the philosophical underpinnings of the Batman's deranged old enemy, the Joker. I also attend some excellent workshops for fiction writers, presented by author Maxwell Drake.

But the most sought-after panels are those headed by actors from popular TV shows, and they  are damn hard to get into. So much time can be spent queuing for a particular room that people will attend earlier panels they're not interested in simply to be in the right place for the panel they  want later.

This underlines the basic paradox of Comic-Con: you could easily spend three times longer in lines than seeing actual programming, and the more popular an item the less likely you are to make it through.

Such heroic queuing is beyond me, but I do sit through a ballroom-sized panel on the TV series Grimm to attend the following panel on the Supergirl TV show.

It's great fun seeing the actors interact and answer questions about their on-set experiences, though they appear the size of ants from where I'm seated. And the Saturday night masquerade in the same venue is entertaining, as fans compete onstage to be named the most impressive costumed act.

While I'm queuing for the masquerade, I chat to Sage Mitchell who has  flown from Portland, Oregon, for the weekend.

"I've been to a couple of smaller conventions, and I wanted to experience the grandfather con," he says.

"It's been great. There's a lot more cosplay here than the small conventions I've been to. It's been like playing Pokemon Snap, chasing people in costumes down and taking pictures. I saw a gender-swapped Jack and Sally from The Nightmare before Christmas, and they did that really well."

If you're not interested in panels, you could spend hours in the Exhibit Hall. It's a vast world unto itself, with stalls selling merchandise from companies big and small.

Beyond the obvious collectables,  I spot stalls with one-off action figures based on unlikely characters such as the late artist Basquiat; steampunk hats incorporating superhero logos; and original art work.

Big entertainment companies are here too, allowing attendees to test-drive their new games or take sneak peeks of upcoming TV series. At the Weta Workshop stand, I hear New Zealand accents as attendees are given monster makeovers by a make-up artist.

Even if you can't score a ticket to Comic-Con, there is plenty to enjoy in San Diego's streets. Running north from the waterfront convention centre is the Gaslamp Quarter, a lively neighbourhood of restaurants and bars. Once a seedy area, this revitalised entertainment hub is buzzing during the big event.

Mitchell has been scoping out the quarter for the big event.

"They transform some of the stores for Comic-Con," he says. "There was one that became Skeletor's Lair, that was pretty sweet. You get a 'power token' first from their Comic-Con booth, then you give it to them to enter the store."

With people spilling out of the convention in all their diverse splendour, San Diego is party central for these four days each July. There's energy, colour, life and joy wherever you look.

And diversity. If the San Diego Comic-Con International is about anything, it's the happiness that arises from celebrating stories and characters in all their varied forms.

"People are very accepting and welcoming," Mitchell says. "Because everyone's here to enjoy their favourite stuff."

TRIP NOTES

MORE INFORMATION

comic-con.org, sandiego.org.

GETTING THERE

Qantas and partners connect to San Diego via Los Angeles. Phone 131313, see qantas.com.au.

Alternatively, Amtrak's Pacific Surfliner train runs from LA to San Diego in three hours. See amtrak.com.

STAYING THERE

The Sofia Hotel, 150 West Broadway. Classy 1920s hotel in a central location. Rooms from  $225 a night. See thesofiahotel.com.

HI San Diego Downtown Hostel, 521 Market St. Budget accommodation in the city's lively Gaslamp Quarter. Dorm beds from  $45, private rooms from  $157. See sandiegohostels.org/downtown.

SEE+DO

San Diego Comic-Con International will next be held from July 20 to July 23, 2017. Four-day attendance costs  about  $267, with tickets snapped up when registration opens months in advance. See comic-con.org.

DINING THERE

The Prado, 1549 El Prado. Stylish restaurant in Balboa Park. See cohnrestaurants.com/theprado.

Cafe 21, 803 Fifth Ave. Colourful eatery in the Gaslamp Quarter, a cafe by day and a bar by night. See cafe-21.com

Tim Richards was a guest of San Diego Comic-Con International and Visit California.