First things first, today's topic will contain spoilers for a title not yet past the year mark, Starcraft II. So if you haven't yet played Starcraft II but don't want anything spoiled for you, then you might want to avoid the further reading button, because some major spoilers are going to be discussed with our topic today.
If you're not familiar with the term Retconning, its short for the phrase retroactive continuity. In other words, it's what usually happens in any sort of story driven medium when the author realizes that she or he has made a continuity error. Let's say you're an author and you've written a wildly successful sci-fi book. Something Harry Potter-ish for the sci-fi world. Now, you're hard at work on the second book, which is proving to be a bit trying since you worked out all of the good plot threads the first go around, when suddenly you get an idea. The second plot would be so much easier if one particular character had been in a certain scene. Then you realize that he could be. All you need to do is remind everyone that unknown to all of them, he saw the entire final battle from the shadows. That is a ret-con. The character was never there in the original, at least, not when you wrote it, but you've engaged retroactive continuity in order to take advantage of the fact that you never specifically said he wasn't there.
Some retcons go as far as to go back to the previously published material and make small changes to support the new development. In this case, if you contacted your publisher and released a modified version of the first book, with extra paragraphs during the final battle describing how no one noticed this extra character hiding in the shadows, then you've taken your retcon to the higher level. You've gone back and changed something that you've previously released.
If you play games, you're no less a stranger to the retcon then any other consumer of media and entertainment. Authors, movie studios, comic books, or any medium with a plot or story (those are different things). In fact, a large reason that we as consumers of a medium enjoy sequels is because we tend to have a suspension of disbelief when it comes to retcons. We ignore the fact that the villains subordinate has come back stronger then ever despite the in-congruence with first ending because we want to be entertained.
Not all retcons are bad either, many just exist to further stabilize an existing story. It's certainly a bit awkward sometimes, after all, a story will stand far better on pillars of it's own merit then hastily propped up material stolen from a prior arc in order to shore a weak point. But sometimes these are unavoidable. Take Valves Half-Life 2 as an example. The first game was a very singular affair. You interacted with numerous characters sure, but only two were ever given a name: security guard Barney and the G-man. When Valve finally released the second game, players were introduced to Dr. Eli Vance and the player is 'reminded' that he was one of the scientists from the very start of the first Half-Life whose life you had saved, and that he and Gordan were long-time colleagues. If you go back and play the first game, no indication is given of this other then some directional dialog (push it into the beam), but Valve retconned that characters role and character in order to give the second game more bite.
Another example of a retcon, and very good one at that, is from the first of Half-Life 2 expansions. As the player is crawling through yet another air duct to open a locked door, Freeman's partner Alyx relates how her father used to tell her how Gordan (the player character) and Barney figured out how large Black Mesa's air ducts were when trying to get into a locked room and how they used to hold races to get into various rooms through the duct system. Its an odd comment, but it suddenly reinforces the behavior of the character you're playing as and gives reason to one of his unusual behaviors, that is the penchant to look for an air duct to crawl through at every opportunity.
The danger of retconning is that like any plot/story device, it can be taken to far and actually ruin elements of the earlier experience. For those who were waiting, now is when we're going to talk about Starcraft II.
Starcraft II had some big shoes to fill. The first Starcraft had a fairly deep amount of lore for it's time as well as a well developed story chronicling a war between three powerful races as well as the various factions and persons behind them. It juggled itself pretty well, keeping the player aware of the plot as it moved forward affecting races, factions and individuals. It also wrapped things up nicely. Tassadar (one of the main characters) sacrificed himself to destroy the Zerg Overmind (a hive mind for a ruthless alien race bent on consuming the galaxy). There was an expansion pack that wrapped up all the loose ends, but left the game open with a question of what the Zerg, with their new leader, would do next.
But this wasn't enough it would seem for the Blizzard team. They wanted the fate of the galaxy to be at risk, and so when Starcraft II finally hit, the storyline contained two extremely poor retcons to support the new plot. The first was the reveal that the Overmind was a patsy who was forced to be the villain in the first game. The Overmind wasn't really bad, it was forced by the real villain to exterminate the Xel'Naga and wage war on the Protoss. Nevermind that the original games manual contradicts this in almost every way. The second retcon was even worse. Tassadar was found by one of the characters still alive in a way, and he actually uttered this line:
"I have never tasted death, Zeratul-- nor shall I."
Wow, way to cheapen the entirety of the first Starcraft's plotline. I enjoyed Starcrafts plot when I played it. I was fascinated by the creepy and malevolent Zerg, and I was entranced when Tassadar made the ultimate final sacrifice and died destroying the Overmind. When Starcraft II made these heavy retcons, a part of that thrill was gone forever and the entire experience was cheapened. Suddenly I was supposed to feel sorry for the Overmind, because hey, it didn't really mean it. Oh, and that whole heroic sacrifice was no big deal, Tassadar's still alive and kicking. If I were to pick my biggest peeve with Starcraft II it was this: that it goes right ahead and throws out a large portion of its established cannon just to make room for a story that wouldn't have worked otherwise.
Blizzard of all people fell into the ultimate trap: They grew so eager to make an idea work that they devalued their previous work completely by drastically changing the attitudes and elements of central characters and events. Therein lies the danger with retcons. They succeed when they play on expectations and assumptions but not facts. Take for example the ending for Portal. Originally Portal ended with Chell blacking out on the surface, and we assume that she wakes up and begins exploring the outside world at some point. However, when the team announced Portal 2, they retconned the ending and extended it so that when Chell wakes up to explore her new world, she's already being dragged away by an Apeture Science bot. Is this a drastic change? Not really, we knew that she had escaped, but anything else we assumed...we assumed. It's still a retcon, but it's one done right.
Retcons are a dangerous tool in any writers book, but I feel that too often game developers feel that they can get away with breaking the established limit more then books or movies already do. We need to reign this in before something goes horribly wrong. We know how retcons can be done correctly, companies like Valve, Bungie and Bioware have proven that. Game Developers need to keep a careful eye on what they do with plots. A little retcon is OK. A lot is not. No one wants to see a "Crisis on Infinite Blizzard" game to clean up all the holes they've made. Then again, that'd probably be pretty cool.