Alternate Universe

An alternate universe, or AU, is a universe that is similar to but not the same as any other given universe--typically because of a few small changes. Any canon universe, and the Real World, can have AUs.

AUs are typically invoked when canon relationships are mucked with (for instance, the common AU where Aragorn never met Arwen and instead spent all his time during LotR shagging Legolas), when significant events don't happen, or don't happen the same way (the AU where the Pevensies don't leave Narnia at the end of Prince Caspian), or where something completely inexplicable has happened (the AU of any canon where all the characters are students at a 'typical Japanese/American/other country high school'). Common types of AUs include:


 * Aforementioned high school AU.
 * Replacing the setting and/or cast of one series with that of another (a type of crossover).
 * Bringing canon characters into World One to act as muses (Trans-Dimensional Snatching).
 * "What If" stories that make some change to canon and explore the logical result:
 * Changing the cast by killing off a character, bringing one back to life or changing an event so they never died, and then writing the story in a different direction.
 * Changing events and following the original canon characters through a new history. For example, the fic might ask, "What if Picard had never been assimilated?" and then follow the crew of the Enterprise to show how Federation history plays out differently. The change is often small, but the effects tend to snowball.
 * Changing events to put different characters in the spotlight--usually OCs or minor characters, but can be major characters in different roles from the ones they usually occupy. For example, a fic that asked, "What if Bilbo had not found the One Ring?" might have the Ring found by orcs or by the Dwarves, changing the focus of LotR to some other group of characters.
 * Fics that take place in the past or future may sometimes be considered AU.

When writing a fic, it is always a good idea to have a good hard think about whether your story is AU or not. Claiming it isn't when it clearly is may result in readers not taking you seriously. On the other hand, labeling your fic AU does not excuse bad writing or poor characterization, so it isn't a free pass to do whatever you want, either. Choose wisely.

Signs You're Doing It Right

 * One basic change is made; the rest of the canon stays intact and reacts the way it usually would.
 * The characters react plausibly to their new situation.
 * If a character's personality is changed, a logical reason exists.

Signs You're Doing It Wrong

 * The existence of one or more Mary Sues.
 * Multiple, random changes that have no common theme.
 * Changes that seem to be contrived for the express purpose of realizing a favorite pairing.
 * Only one result of a change is explored--all the others are ignored, even when there should be widespread effects.
 * Characters share only their names with their canon counterparts.

AUs and the PPC
AU stories are not immune to the attentions of the PPC just because they are marked AU. If a canon character is OOC in ways not explained by the changes in the fic; if there is horrible writing present; if there are Sues, bad slash, an illogical plot, or any other signs of badfic, the PPC can and will send agents into AU fics. In fact, the Department of Improbable AUs handles AU fics exclusively, the Department of Implausible Crossovers handles crossovers, and Despatch handles cases of Trans-Dimensional Hopping and Snatching.

According to one version of Multiverse Theory, AU continua are part of the Multiverse. Just like there are multiple versions of World One, there are multiple versions of each continuum because a story is never just made of the events in the story--it is also made up of the events that could have happened, but didn't. These "could have" worlds are AU versions of that continuum, some more likely than others, and badfic in these worlds can endanger the canon just like badfic that directly affects the prime version of that continuum.