1. Mei is pretty happy for having such a horrible life
Though Overwatch takes place 60 years in the future, most of the world's important events happen decades before. Many of the game's heroes were around during both time periods, and have aged accordingly; that's why we have an assortment of grizzled old dads like Soldier 76, Torbjorn and Reinhardt. Some of them had a little bit more going in the intervening years, like Mercy (we'll get to her soon). And then there's Mei. By all rights, Mei should have hit menopause by now, but she still looks like an insufferable millennial. There's a good reason for that, and it might make you feel bad for hating her so much.
See, about 30 years before the game takes place, Mei-Ling Zhou was working in Overwatch's Anarctica station. As a scientist, she and her team were working to figure out the true cause of the planet's rapidly-worsening weather. They didn't get too far, because irony hit the base hard in the form of a massive polar storm. Life-sustaining supplies running low and no hope for escape, the scientists hopped in cryostasis pods as a last-ditch effort to survive. Every person at the station lay in hibernation, hoping that someone would arrive to help soon. That help never arrived.
Decades pass. The ruins of the station were finally rediscovered, and Mei was the only one whose cryo-pod was still functioning. Every other one of her colleagues had perished in what we can only imagine is a pretty hellish demise. One after the other, they likely woke up after the life support systems failed, alive long enough to realize they were trapped in their own pods, with nothing to do but gaze at the dead, or worse, those living that were still sleeping.
Mei awoke to a changed world, one without Overwatch and with an even worse climate than before. But she didn't let that get her down.
Maybe the most remarkable thing about Mei is how she seems to keep a positive outlook on the world, despite the horrible things that have happened to her. All of her co-workers died, and she missed out on what should have been the prime of her life. And yet, she still starts matches saying things like "The world is worth fighting for!" At heart, Mei just wants to make the planet a better place. Sometimes that means freezing a Genji and staring at him like a deranged serial killer before impaling his head with a giant icicle.
2. The Omnic Crisis is just a fancy word for "Judgment Day"
Overwatch isn't just your run-of-the-mill ragtag group of well-meaning vigilantes. They were originally assembled in an official capacity as a direct response to the Omnic Crisis. For a while there, humanity was living pretty peacefully with consumer-grade robots called the omnics.The original intent for these omniums was to "bolster manufacturing and create economic equality worldwide." But the company behind these robots, the Omnica Corporation, wasn't exactly on the level. When it was discovered that their plans included lies, fraud and other hornswagglery, Omnica was shut down and their 'bots were de-activated. The omnics were understandably a tad upset about this. Imagine if you were born with a great purpose, one that would help build paradise on earth -- and then suddenly everything was canceled and you were set for termination, just because your dad was kind of an asshole. That's what the omnics were going through.
Of course, because Terminator movies apparently don't exist in this world, nobody sees the violent AI uprising coming. The de-activated omnics went ahead and re-activated themselves, then began gathering arms by hijacking military equipment and repurposing giant mechs for what giant mechs were always meant to do: Fight everything.
Things were pretty dire for humanity. On a scale of "threats that might wipe out human existence," the Omnic Crisis was somewhere above the Cold War and just one notch below those KFC Double Downs with hot dogs inside. It was around this time that Overwatch came about, formed as a strike team to combat the omnics. This appeared to be working out pretty well, but the new squad had their work cut out for them.
A lot of it has to do with the fact that the omnics were built in these special factories called omniums. The Omnica Corporation had set these automated, self-sustaining robot mills up all over, and what was once convienent came back to bite the planet in the ass. Since the ominiums were designed to not only run themselves, but also constantly improve themselves and the robots coming off the assembly, this means the human-hating omnics in control of the operations had a never-ending supply of soldiers that were growing steadily more powerful. If you think Bastion was a real piece of shit before, omnium-ized Bastions basically have two Mercys while being shielded by three Reinhardts.
So why not just blow up these factories? Well, someone did, and that's how we got these dickbags:
Eventually, the Omnic Crisis ceased and an unsteady peace was declared. Australia in particular gave its omnics a swath of land to build on as part of the settlement. But the locals weren't thrilled with their new neighbors pushing them out of what was once their home. The Australian Liberation Front came together to fight against the omnics, and with the help of the man who would become Roadhog, they destroyed the main omnium on the continent. They didn't really think that part through. Omniums are fueled by fusion cores, and when these are destroyed, the surrounding land mass becomes a nuclear wasteland.
It was out of this Mad Maxian hellscape that a scavenger named Junkrat met a newly-deformed Roadhog, and the two went on to become international criminals. This is what you get when you don't play nice with robots.
3. Mercy saved Genji (and created Reaper)
Like many other members of Overwatch, Mercy has been around since the old days. But she doesn't have a proper excuse for looking like she's just out of college while simultaneously pushing 40; the whole "frozen in a cryogenic chamber" origin story was already taken, after all. Mei even makes comments in-game about how Mercy doesn't look a day older than when she last saw her, before the deep freeze. There's probably a little more going on here than just immaculate Swiss genes, and it might have something to do with Mercy's profession. As a "medic class," it only makes sense that Angela Ziegler would be the Overwatch team's resident doctor.
As nice as it is to be on the recieving end of Mercy's healing beam, it could be argued that she takes her incredible medical knowledge a little too far at times. Just ask Genji.
As you might know if you've seen the stellar animated short Blizzard released, Genji was once part of the Shimada clan. For the longest time, Genji was kind of a terrible ninja, forgoing his training in favor of living it up in the lap of luxury. This brought him in conflict with his older brother Hanzo, who was always on Genji's ass about pulling his weight in the family. Everything came to a head after their father died, and an ensuing argument lead to a fight which in turn led to Genji clinging to life. Hanzo had actually assumed his brother was gone, but it was Mercy that brought him back from the brink.
With the help of Overwatch, Mercy and her team outfitted Genji with advanced cybernetics which allowed him to systematically tear apart the Shimada clan and their criminal empire. But after his revenge was complete, there wasn't really anywhere for Genji to go -- humans reviled him for being half machine, and he wasn't exactly at home with the omnics. It was only under the mentorship of Zenyatta that Genji came to grips with himself and his new form.
Mercy has... something of a habit of playing around with people's lives in the interest of science. Exhibit B: Reaper.
Like Genji, Gabriel Reyes also had a brush with death before being "saved" by Mercy. Seemingly killed in a fight with Soldier 76 (we'll come back to that), Reyes later resurfaced with a new look that's part Skeletor, part Dracula and 100% Edgelord. Now known as Reaper, Reyes engaged in terrorist acts across the world, leaving strangely drained bodies in his path. It became clear that Reaper's cells were rapidly decaying at the same time that they were rapidly regenerating, leaving his body in a nebulous state of limbo -- those dessicated corpses in Reaper's wake are likely a result of him sucking their life force to stay stable. This is actually represented during matches, since Reaper can consume the "souls" of fallen foes to regain health.
Who says Mercy had anything to do with this? Well, Reaper certainly seems to think so, according to an in-game exchange.
Mercy: What happened to you?!
Reaper: You tell me, Doc.
Mercy: This is not what I intended for you, Reyes.
Reaper: You knew exactly what were you doing.
This would appear to imply that Mercy had a hand in Reyes' ressurrection. It makes sense, since Mercy specialized in nanobiology. Whether or not she went too far in her work to bring back an old friend still seems unclear. Either way, all will be forgiven if she'll just tell us what skin cream she uses.
4. The assassination of Mondatta
In another animated short called "Alive," we learn a little more about Widowmaker, the unrepentant sniper who works for a terrorist organization called Talon. The featured mission: Kill the omnic leader Tekhartha Mondatta. A friend of Zenyatta's, Mondatta had come to the human/robot tension powder keg that is King's Row in order to soothe relations between the two groups. Mondatta and his group, the Shambali, believed that every omnic had a soul, and wished to live in harmony with humans. That didn't stop Widowmaker from icing him all the same.
Immediately after the assassination, Tracer tackles Widowmaker and demands to know why. Why would anyone want to kill robot Gandhi? For Widowmaker, the answer is probably simple: She enjoys the act of murder. It makes her feel alive. But her organization Talon obviously put her up to the job, and it's still not exactly clear what their endgame is. Why destroy a chance at peace for humans and omnics?
There might be any number of reasons for such a hit. Maybe Talon figures the more chaotic an environment, the better. Maybe they have a financial interest in keeping the world at war. Maybe they just really hate robots. If that was the case, their plan didn't exactly work, since a statue of Mondatta now stands near the place where he was killed.
In death, Mondatta became a martyr for a righteous cause, likely becoming much more effective as an iconic figure than as a mortal being. Which, in retrospect, was a pretty predictable outcome. Maybe these Talon guys really do want to make the world a better place. With bullets.
5. The Fall of Overwatch
The entire premise of "heroes regrouping after a long time off the job" relies on the fact that the band had to first break up at some point. That definitely happened to Overwatch, but it took many years and a variety of problems to finally bring them down. A big component was the public, who -- at least, for a while -- loved Overwatch. They had saved the day during the Omnic Crisis, and had gone on to do great things. But leading up to their dissolution, Overwatch's popularity had been fading for some time. There were a lot of serious accusations thrown their way, rumors of corruption and murder that the organization just couldn't shake. Most of the controversy centered around Overwatch's covert ops team with a creatively-bankrupt name: Blackwatch.
Right away, Blackwatch had a big problem, and his name was Gabriel Reyes. Though they technically were on the same team, Reyes had a big beef with John Morrison, ever since the latter had been promoted to Overwatch's commander. The team's version of Slash and Axl Rose, the two were at odds until the very end. The existence of Blackwatch had just been revealed to the public when Overwatch's Swiss headquarters was mysteriously destroyed.
The in-universe media isn't clear on just what brought the building crumbling down, but it's pretty clear to us what happened: There was a mutiny within Overwatch, and the resulting civil war destroyed the group from the inside. Morrison and Reyes were supposedly "killed" during the event, but we know they both live on as Soldier 76 and Reaper, respectively. This marked the end of an era, and the team disbanded.
Though most of the remaining members scattered to the wind, there were others that seemingly joined the side of the terrorists. Jesse McCree ran afoul of several Talon operatives in a special comic, and noted that they were using tactics once utilized by Blackwatch . He should know, since he used to be a part of Blackwatch himself.
That Talon has its hands on the Blackwatch playbook shouldn't be too surprising, since Reyes is now among their ranks as Reaper. But it makes you wonder just when that flowing black coat turned.
Of course, we know that Overwatch reformed, though now it's unsanctioned by the UN and wholly illegal. Now that the new team seems to be free of the bad apples that plagued its first iteration, they can get started on making the world a safer place without worrying about internal politics. First item on the agenda: Escort this floating truck for like 500 yards.