Have you been Jossed? It can happen to anyone at anytime and anywhere-- providing you are role playing or writing fanfictions based on a TV show, movie or books that takes place have a series format.
This term is named for Joss Whedon, the creator of Buffy the Vampire Slayer. Originating in fanfics but able to carry over into rpgs, "getting Jossed" refers to the moment when something you've written is completely invalidated during the course of the series. Say that you wrote that your character is the child of Spike and Druscilla but then we learn that vampires can't have kids-- except that one time Angel and Darla did but that doesn't count. Anyway, you've been Jossed because unless the circumstances are special, there is no way in Hell that Spike and Dru could naturally have a vampire child.
Sometimes a series will forget it's own bible, have a brain fart or just decide to totally change an established story or fact to make it go into a different direction. On Buffy, when Angel and Spike get together for the first time on screen Spike is blathering on and on about how he's disappointed that Angel seems to be good now and he says Angel was his sire. He looked up to him like a father after Angel turned him into a vampire taught him about how to stalk and kill people.
RPGs and fanfictions all over the internet were writing stories about the stalking days of these two when, oops! Joss Whedon went and made an episode where Spikey boy was actually sired by Druscilla. Technically this Jossing was Joss' fault but every Jossing since has been due to overzealous writers in rpg and fanfiction forums.
Jossed by J.K. and Others
Since getting Jossed can happen with any medium that is a series, we can look at the Harry Potter series where lots of Mary Sues were deeply shocked about a certain fact that they'd all guessed about. A character was introduced to the story named Blaise Zabini. The only information that readers were given was that Blaise was a Slytherin. Shortly thereafter, fanfictions and rpg sites were crammed with characters named Blaise Zabini who was hot, gothie Slytherin chick that wanted to jump Draco Malfoy. But then Harry Potter and the Half Blood Prince came out and all those characters were rendered obsolete. Turns out Blaise is a black boy who doesn't exactly agree with anything Draco Malfoy says.
In every series there are other forms of this term but the most common word I've seen is Jossed. Dr. Who fans like "Russeled" after Russel T. Davies and perhaps some Harry Potter fans like the term JKed. I think I just like the way it sounds to yell, "Dude, you've been Jossed!"
The Other (and Way Wrong) Definitions
There is a bit of controversy about the meaning of getting Jossed but any other definition that's different from the one I gave you is wrong. Because I say so. And many people agree with me. So there.
Some purists believe that instances like the one I mentioned with Spike not being sired by Angel is the true meaning of being Jossed. That would make it even more rare and less likely to give you moments of pleasure when pointing and laughing at another person who has been Jossed.
The most absurd theory is that getting Jossed has an almost opposite meaning. Some morons think that getting Jossed is when the writers of a series are actually out scouring the forums, reading fanfictions and rpgs and getting ideas for the series because they have no imaginations of their own. Right. If you say that Angel could smell Wesley on Lilah and then on the show Angel says that to Lilah, it just means that it's not out of the realm of possibility to believe that vampires have super sniffers and can smell sex on a person. If you're patting yourself on the back because you guessed that Harry Potter would have a son, remember that if Harry Potter were to have child, there is a 50% chance it will be male and J.K. didn't actually get the idea for that by reading your story online.
Then What is Whedoning?
Whedoning is not to be confused with getting Jossed. It's an entirely different thing. Whedoning occurs when something incredibly awesome and squee-worthy happens to a character and then they are killed in a horrible, crushing way. Tara McClay was Whedoned on Buffy when she got back together with Willow and they had sex all night long and in the morning Warren accidentally shot Tara dead.
Getting Jossed is Part of a Journey
Don't get sad if your hopes, beliefs, theories and wild imaginations are proven wrong. So what if your character becomes a part of a alternate universe rather than part of canon world? It's all a game and playing a character that no longer exists or using an idea that is not based in fact anymore brings more unpredictability to the plot lines. If it happens to you, just roll with it. If nothing else, it will free your character up for greater things later on.