Often abbreviated to ASB, this is a term given to a subgenre of alternate history concerning points of departure which aren't actually based on the course of factual human history. These include alternate history scenarios based on fictional or fantastical worlds, and more contentiously, on deviations in the evolution of life on Earth and on the Earth's geology. Simply put, any sort of event or timeline which would be impossible, or ludicrously unlikely, without divine intervention or “the activity of alien space bats”.
The name predates AH.com and comes from the now defunct alternate history site/newsgroup Soc.History.What-If. One of the main creators of the term was the late, great Alison Brooks, a British member of said site and long-term AH fan. This hasn't been overlooked in more wider fiction-writing and fiction-reading circles, and the term even appears on Wikipedia. Ken MacLeod's 2005 SF novel Learning the World outright uses the ASBs as side characters and an in-joke part of the novel's cast.
The wide umbrella of ASB includes scenarios involving magic and, by AH.com convention, also any AH writings based on divergences from existing fictional universes, such as Star Wars. Nowadays, this particular subset has its own separate forum, though in the past it was lumped under the ASB forum.
There is a heated debate as to whether scenarios that involve small or large geological changes in the world count as ASB or not. A good example of such a geological change is the eponymous island of the Tarrantry series. As a rule of thumb, AH.com administration considers geological PODs and works with such PODs to be a form of ASB scenario, so they should be posted in the ASB forum.
“Without wandering into some of the more interesting aspects of Chaos Theory and philosophy, ASB can be fairly well defined.
There are other, less well defined parameters as well. What ASB is NOT is a dumping ground for poorly thought out or flat out dumb threads.”
The last sentence is of special importance, since many AH.commers feel that the very term “alien space bats” has deteriorated over the years - or more precisely, been cheapened in its meaning. Often, a member of the board will claim that some odd historical or current event is ASB just because it is odd. This is not a proper use of the term. Just because a certain event is odd or seems somewhat unlikely doesn't mean it can't happen at all, as long as it doesn't break the laws of physics, the very nature of our universe or doesn't involve a random and blatant outside factor. Odd stuff is at worst improbable stuff, but ASB stuff means that it's outright implausible/impossible stuff.
Say, a military coup in a small African country happening under odd circumstances is just that : Odd. Unless either side of the coup explicitly gets ISOTed away to somewhere or receives hi-tech guns from time travelers or aliens paying a visit, said scenario is not considered an Alien Space Bats scenario. Now, if any of those three strange events (physics anomalies, time travel, alien invasions) occured in said scenario and interrupted the course of the regular world, it would definitely be an ASB scenario.
1.) ABC versus XYZ: Basically one group of individuals with an unlikely combination of capabilities versus another group of individuals with an unlikely combination of capabilities. For example Lesbian Vampire Pirates versus Nazi Werewolf Cheerleaders.
2.) Guns of the X: Derived from Turtledove's novel Guns of the South, in which a South African Neo-Nazi group from the 21st century uses time travel technology to travel to the 1860s and arm the Confederate States of America with AK-47 assault rifles, thereby allowing the CSA to win the American Civil War and be used as the basis of a white supremecist state. Similarly in a Guns of the X scenario a country or group under threat is provided with future weapons which will allow them to overcome their adversaries. Guns of the X threads include but are not limited to:
3.) All X/Non-X Dissappear: All persons within a certain group, nation or race dissappear, or all persons outside that group, nation or race dissappear. The thread then discusses how the remaining members of the human race handle this event.
4.) You Wake Up…: In this scenario the reader is told that when they awaken in the morning they find that some sort of reality modification has occured during the night. The most common theme is that the reader wakes up as a historical personage on the day of a major life changing event, for example: You Wake Up As Julius Ceasar On The Ides Of March. Sometimes the reader is not placed in the body of a specific person but rather as themselves but in a new role, for example: You Wake Up As The President of the United States on 9/12.
Other popular variations of this scenario include having the reader wake up as themselves but in a different physical body, ie: younger, older, the opposite gender or another race, having the reader wake up to find their family life changed, ie: married with children, having a twin or even being their own twin, having the reader wake up isotted to an ATL.
5.) X ISOTs To Y: In which a person, territory, object, etc. is transported from one place and/or time to another, usually examining the immediate aftermath. A long-popular subject for timelines.
6.) The Race Invades X: Derived from Harry Turtledove's Worldwar series, in these scenarios the alien Lizards invade a different setting or time period. Originally a trend in the Alien Space Bats forum, timelines with this subject have since shifted over to Fandom AH since the creation of that forum.
In recent years the ASB forum has developed something of a reputation for frivolous, creepy or careless threads. After several earlier abortive attempts to do something about this, the Landshark Offensive was launched in 2009. Since then, the forum has gotten much better again. The introduction of threads created specifically for frivolous and non-frivolous ASB scenario ideas has had a fair share in improving the situation.
The Alien Space Bats have appeared as powerful villains in the AH.com The Series, first openly mentioned in the episode AH.COM THE SORTA-KINDA-MAYBE NEXT GENERATION. They have since appeared as recurring antagonists throughout the series, as well as its other sequels and spinoffs set in the “AH.comverse”.
ISOT - The “mass teleportation” type of ASB.
The ASB Forum - Where scenarios like this show up.
Soc.History.What-If - The lads and ladies who coined the term.
Bats - Other references to our furry winged friends.