Final Fantasy XV enjoyed a widely positive reception when it launched in December.

As it should — it's an expansive world filled with likeable characters that is being rightly praised as a return to form for the venerable Japanese video game series.

Yet there are times when things don't quite go right.

A FFXV player has posted a screenshot on Twitter that shows one character's head sticking out of another character's stomach. There's no blood, and the characters don't show any signs of distress, because this — let's call it an "incident" — wasn't intentionally programmed.

The 3D models have simply crashed into each other, like one of Picasso's cubist works of art.

Thank god FFXV was delayed a few months ago to correct any weird bug. <a href="https://t.co/A4qZO6N74n">pic.twitter.com/A4qZO6N74n</a> —@KathrynGamer

The game offers a host of other examples — heads sticking out of car roofs, bodies swimming in mid-air and characters being flung into the sky for no obvious reason.

What we're looking at are glitches — unintended consequences of the complex code and algorithms that give life to virtual worlds.

Over the decades, glitches have become a source of unintentional humour and deep fascination for gamers.

'It feels like breaking the rules'

"Usually, it's best described as an oversight, something the game developer didn't expect you to do," says Andy Collins, a YouTuber who documents game glitches on his video series Son of a Glitch.

Before sites such as Wikipedia and GameFAQs documented the finest details of any given game — including secret items, level skips and even bugs that have since been addressed by software updates — glitches were urban legends, disseminated by word of mouth during recess at school.

Jumping through a solid brick wall in Super Mario Bros., allows you to play the Minus World, a glitched-out level that never ends. (Nintendo) Toronto-based game developer Benjamin Rivers says he has fond memories of "the Minus World," a glitched-out area in Super Mario Bros. for the Nintendo Entertainment System. Anyone can access it by making a very specific jump through what is supposed to be a solid brick wall.

"I reproduced it many times, but like many other players, when getting it to work, I couldn't help but think, why is this here? It has to mean something!" he says.

"So I'd imagine what the Minus World was, and why it existed — it would keep me up at night, knowing deep down that it was part of an equation [in the code] that couldn't quite be resolved."

Collins says his interest in glitches began with the speedrunning community — that is, players who try to finish video games in record time, sometimes by using clever exploits in the code to skip entire levels or areas.

Some speedrunners have spent years trying to figure out how certain glitches work in order to fast-forward to the end credits, in the process skipping entire levels.

YouTuber Andy Collins produces a series of videos, called Son of a Glitch, that focus on documenting and explaining glitches in video games. (CBC)

For example, by finding and jumping through a magical barrier that's supposed to be completely impenetrable, players have managed to finish The Legend of Zelda: The Wind Waker in less than four hours. Collins says that playing through the game the way it was intended should take at least 10 hours.

Collins says there's a unique appeal to discovering game glitches and learning how to reproduce them. It's akin to dismantling an old radio or home appliance to better understand how it works, he says.

"It feels like breaking the rules, and there's a certain kind of oh-wow-I'm-not-supposed-to-be doing-this element to it," he says. "It's almost as if you're expanding on the game in some way."

Game-breaking bugs patched out

While many gamers have developed an interest — and even formed entire communities — around glitches, responses from publishers have been mixed over the years.

Glitches that actually impede play can dampen the coverage of a new release. Look no further than Ubisoft's Assassin's Creed Unity, from 2014.

Critics gave Unity's story and gameplay a lukewarm reception, but were even harsher on its litany of bugs and glitches, the most striking of which involved characters' faces showing up as mangled shards of polygons and floating eyeballs during what were supposed to be emotional cut scenes.

The reviews were quickly overshadowed by Ubisoft's apologies for releasing the game in such a buggy state.

Ubisoft's Assassin's Creed Unity suffered from glitches both game-breaking and hilarious, including mangling characters appearing without skin on their faces. (Ubisoft)

Thanks in part to changes in the way games are played and updated these days, glitches don't have the same kind of life they did in the 1980s and '90s.

Severe, game-breaking errors can be ironed out and delivered via an online update, or "patch." Assassin's Creed Unity, for example, runs far more smoothly now than it did at launch.

Glitches embraced in culture

Glitches both good and bad have in some ways become canonized as part of the medium, as developers embrace the humour and memes that grew out of them.

Take the 2015 fantasy game The Witcher 3. In it, the hero Geralt can whistle to summon his horse Roach, only to find it inexplicably floating in the air, or standing on the roof of a nearby building.

Polish developer CD Projekt Red took it in stride, incorporating this gaffe into their upcoming card game spinoff Gwent. Roach's card depicts him gazing down at a perplexed Geralt from said rooftop.

Axiom Verge features retro glitch-like visuals as a love letter to their presence in older games. (Thomas Happ Games)

Then there's Axiom Verge (2015), designed as a love letter to eight-bit games from the '80s such as Mega Man and Metroid.

One of the character's most powerful weapons, the Address Disruptor (or "glitch gun"), scrambles any enemy or item in its sights, blowing it apart in a flurry of misaligned pixels and radically changing their behaviour.

The bug had literally become a feature.