There are a lot of famous video game franchises out there -- the whole Super Mario universe, everything Pac-Man, Sonic the Hedgehog, Diablo, and many, many more. Outside of puzzle games like Tetris, most of these games follow a similar format: you’re the hero, striving to achieve an objective while avoiding (or successfully fighting off) bad guys. And then there’s Grand Theft Auto, commonly called simply "GTA." The franchise -- one of the top-selling of all time -- flips the old “cops and robbers” tale on its head; you’re the robber, running from the cops. It’s not the first game to do that, but it’s easily the most popular.

And we only get to play it because of a weird programming bug.

The first Grand Theft Auto game debuted in the winter of 1997, to mixed reviews -- many industry experts found the graphics to be nothing special, the way you controlled your car wasn’t so clean, and the objectives given to the players weren’t all that challenging. But the developers of the game, DMA Design (now “Rockstar Games”), weren’t all that concerned, particularly with that last issue. They designed Grand Theft Auto to be an “open-world” game -- players don’t need to accomplish any of the missions to enjoy the game; they can just drive around, doing whatever, until their real-world obligations require them to turn the game off. And the DMA Design team had good reason to think that players would do exactly that.

The reason? The way they originally built the game was different -- and it wasn’t fun. At least, not until the game itself broke.

“Grand Theft Auto” was originally pitched under a different title, “Race’n’Chase.” According to an early proposal for the game (here’s a pdf), there were four different modes, and yes, in one of them, you got to play as a bad guy -- a bank robber. That was a key addition; according to PC Invasion, “originally, DMA had thought to put players in the role of the police, but there were inherent issues with this. For example, if there was heavy traffic, only the criminals could choose to drive on the sidewalk and run down pedestrians. The concept got scrapped because no officer could conceivably do this.” 

But even then, the game was boring. In an interview with Gamasutra, Gary Penn, one of GTA’s designers, noted that "it didn't really have much -- it had an odd structure at the time and it was very much a traditional mission-based thing.” Once you finished a task, the game became quickly repetitive. It simply wasn’t close to ready for release, and DMA Design considered shelving the game altogether. And then something went wrong -- or right, depending on your point of view. Penn continued: “O]ne day, I think it was a bug, the police suddenly became mental and aggressive. It was because they were trying to drive through you. Their route finding was screwed I think and that was an awesome moment because suddenly the real drama where, ‘Oh my God, the police are psycho -- they're trying to ram me off the road.’” 

The bug wasn’t intended, of course, but it was fun -- and it was enough for DMA Design to rethink Race’n’Chase entirely. As GameFAQs reported, “This glitch turned out to be the shot in the arm that the game needed. Suddenly, every chase was a life-or-death struggle against a psychotic army of suicidal police cruisers who would stop at nothing to turn your car into a twisted heap of burning scrap metal by any means possible. The playtesters started ignoring the missions and the dev team discovered that messing around in the open world was often more fun than following the game’s story.” 

The police were made less crazy in the final game -- they’re officers of the law, after all, and can’t be doing more damage than they prevent -- and GTA does have missions in the final product. But for many games, those missions no longer mattered. A top-rated review on IMDb sums it up: “I remember I once played this game for 5 hours straight and I still could not get past the first level. But for me, most of the time, I'm having so much fun killing people and smashing up cars that I don't care about the missions.” Being the bad guy in a world that allowed it was its own reward.