POSSIBILITY ENGINE is a fanfic that takes the premise of Sliders and applies it to Kim Possible. The story begins with one of Drakken's devices malfunctioning and ends with the first battle in an interdimensional war. Throughout it all, Kim and Shego form an uneasy alliance as they jump from world to world trying to find their way back home.
The story is notable for making dimensional travel accessible and easy to understand, while still engaging in a level of pseudo-scientific Techno Babble that's enough to keep any Speculative Fiction fan interested (one of the chapters is, in fact, called "Technobabble"). The author is very good at conveying the sense of shared isolation that would naturally result from an interdimensional journey, while still hinting at grander things and building an obscenely complicated plot that requires multiple readings to understand.
There is a sequel, called The Demon of Go City, that unfortunately hasn't been updated in a while. It has also spawned two side stories, Contagion and The LAST Thing You Wanted to Read, the former of which ties the series into the author's Disappearing Doctor Universe, while the latter is a non-canon "what if" scenario in which Ron has somehow become Deadpool. All are very much worth checking out.
This Fanfic provides examples of:
- A.I. Is a Crapshoot: Pentos/Athena. Played with, since she becomes a lot more confident and able to think for herself, but still remains fanatically devoted to The Grand Commander and his wishes.
- Armor-Piercing Question: When Zorpox gives his Motive Rant near the end of "Slow Collapse," Kim reveals herself and asks him: "Is that why you're doing this, Ron?" The shock of seeing her and realizing he was wrong completely breaks his resolve.
- The Atoner: While she doesn't execute a full HeelFace Turn, Shego's experience in the first world leads her to not be so reckless as the version of her that created such a hell.
- Bittersweet Ending: Let's see: The Grand Commander has just launched the opening salvos of his war on the multiverse, stolen the Infinite Drive Matrix, and is preparing for his next move. Athena has taken over Kim's body, and The Agency has lost a lot of its people. On the other hand, Shego is now more determined than ever to get Kim back, and the story ends with Fayt showing up to try and fix things.
- Chekhov's Gunman: Fayt, the girl from the fanfic Ron tries to write at the beginning of the story, which according to the rules of the multiverse means that she now exists and is working to fix everything.
- Cold-Blooded Torture: Shego is on the receiving end of this in the first world they go to, since Drakken, Monkey Fist and Killigan still have some issues to work out over how The Supreme One treated them. The experience sticks with her for the rest of the story.
- Cold Open: A couple of the chapters have a short scene before the title is revealed.
- Create Your Own Villain: Shego unwittingly inspires Pentos—a shy, demure AI who only wishes to serve The Grand Commander—to become Athena, an evil, sadistic, power-hungry bitch.
- Deadpan Snarker: Shego, of course.
- Enemy Mine: Kim and Shego for most of the story.
- Facial Dialogue: Though she does know how to use words, this is primarily how Cassie communicates with Shego. Dr. Kim and Ron even lampshade it at one point.
- For Want of a Nail: Every world that Kim and Shego visit usually has one or two major events from which all other changes stem. Kim eventually learns from another version of herself that the reason each world they visit is so different, rather than just minor changes like a different outcome of a chess game, is that alternate worlds tend to cluster around a main hub world where the biggest change took place, and without specific targeting, interdimensional travelers will usually end up in the main world.
- Grand Theft Me: Athena does this to Kim, downloading herself into her brain.
- He Who Fights Monsters: M, a version of Monique whose parents were killed by the mob, and who has dedicated her life to taking them down. In the process, she's done some things that essentially make her no better, which includes breaking Wade's legs when he pointed this out.
- Interdimensional Travel Device: The Pan Dimensional Vortex Inducer. After visiting the first world, an alternate version of Wade develops the Trans-Dimensional Facilitator, or TDF, combining PDVI tech with the Kimmunicator to give them a more easily controlled version. It can only open gates once every 24 hours.
- Meaningful Name: The Grand Commander's AIs are all named after figures of Greek mythology.
- Zelus is the personification of dedication and emulation.
- Asclepius was the demigod in charge of medicine and healing, an appropriate moniker for the AI in charge of The Grand Commander's health.
- Cratos was the personification of strength (no, not that Kratos—he was actually a demigod), which is a fitting name for The Grand Commander's head of security.
- Prometheus is well known as an immortal who brought fire to the mortals, and was imprisoned by the aforementioned Cratos at the behest of Zeus as punishment. This is actually a clue, since he has been supplying information to Kim Possible's underground resistance movement.
- Athena was born when Zeus ate one of his mistresses (no, really) and she burst fully formed out of his forehead, making her literally Zeus' brainchild, which is fitting for an AI. She was also the Goddess of Wisdom and Defensive Warfare, which makes her name somewhat ironic as well considering this Athena's actions.
- The Multiverse: The primary concept at work.
- Reality Bleed: Drakken's plan at the beginning is to use the Pan Dimensional Vortex Inducer to find a reality in which he was able to conquer the world, then use a device called a Dimensional Drill to let that reality invade this one. It doesn't work.
- Ridiculously Human Robots: The MFRs.
- Self-Fulfilling Prophecy: The Grand Commander's dimension was imprisoned by another because a version of Kim came from a future where the GC had taken over the multiverse. Guess what he tries to do after learning this?
- Techno Babble: This being a story about interdimensional travel, of course not everything is going to be perfectly scientifically accurate. It is, however, all internally consistent and easy to understand. Funnily enough, one of the chapters is actually called "Technobabble."
- Villainous BSoD: Shego goes through one on the first world, when she witnesses firsthand what would happen if she took over the world, because the events of A Sitch in Time didn't erase the timeline, simply created a new one. It turns out that Drakken, Monkey Fist and Killigan still have some issues over The Supreme One's treatment of them, and they torture her using a shock collar. More than anything, however, she is disturbed by the fact that on some level, she wanted this world at times. It continues to haunt her throughout the rest of the story.
- Well-Intentioned Extremist: Three of them, right in a row, and all with escalating levels of desperation and nastiness. M is a version of Monique who has essentially become no better than the Mob who ruined her life, Ron becomes Zorpox and tries to attitudinate the world after Kim dies, and The Grand Commander starts an interdimensional war over his obsession with finding another version of Monique, who died in his world.
- Wham Episode: "Technobabble" and "War of the Worlds, Part III."