Two worlds exist and the physical laws or geometries of one bleed over into the other.
This usually takes one of two forms:
- A world with overly simple rules and internal logic entered by somebody from an Earth-like world. These works are more prone to humor as the native inhabitants fail to understand or loudly disbelieve things which would be obvious to normal humans.
- A world which has an alien set of physical laws (or somebody from it), that then interacts with an earth-like world. Type II worlds are almost always in the horror genre. Visitors from these worlds are often either The Fair Folk or Eldritch Abominations.
Although this sometimes overlaps with Alien Geometries, it is not about the alien shapes involved (although they can be a side-effect) but rather the idea that something is invading a world by sending their laws of physics first.
The litmus test for being this trope is:
- There must be two independent worlds.
- Something must cross from one world to the other.
- The "laws" of the invading world must work in the invaded world. (For example: if a mage comes from magical world A to mundane world B, it only becomes this trope if the mage can cast magic in the mundane world where magic is normally impossible.)
May happen between Layered Worlds.
Simple worlds invaded by "real world" elements
- In Doctor Strange (2016), near the finale, the main character introduces a normally timeless character to the concept of time he explicitly brings with him from Earth. The prospect of being stuck in an endless time-loop is so terrifying that the big bad agrees to leave the Earth in peace and take his minions with him.
- In Pleasantville, the protagonists are high school students from our world who enter the world of a black and white 1950s TV serial, in which everything is excessively pleasant and patterned after '50's moral standards (besides colour, there's also no rain, crime, homelessness, fire, sex or toilets). Throughout the film the protagonists' actions impact the world around them and colours and concepts from the real world (like fire, sex and rain) start to appear as a result.
- In Flatland, A Square is visited by a sphere from the mysterious dimension of "up" and interacts with the strange world of the third dimension. A sphere manifests as a circle that grows and shrinks, able to bypass all flatlander doors and walls and even touch "inside" a flatlander. The protagonist eventually learns to think multi-dimensionally and is considered insane by most. What makes it this trope is subtle, when taken from one dimension to another (for example when he is in the 3-D world), the normally 2-dimensional A Square is able to perceive higher and lower dimensions. (So in the 3-D world he can see the interior of 2-D people.)
- Erfworld: The world's rules reflect those of a traditional turn-based tabletop game. For example, terrain is divided into hexes and units can only move a certain number of spaces each turn.
- The protagonist is from Earth. He experiments with the physical laws of the world in an effort to better understand the rules of the game and attempts to cheat with them (even without cheating, mastering the system makes him a tactical genius). He also appears to have several interesting and unique properties that are a hold-over from reality (such as a lack of visible stats, blood, and the ability to get distracted and forget direct orders).
Earth-like worlds invaded by alien elements
- In the Judge Dredd story "Helter Skelter", interdimensional travel by supervillains from other universes starts to fracture the fabric of reality, causing elements from different dimensions to bleed over into each other. One alternate dimension in particular is referenced that collided completely with another one, merging the two into a never-ending World of Chaos.
- In The Conversion Bureau, Equestria has been transplanted to Earth in the future, not too far off the shore of the USA, by forces unknown. Its magical field is slowly expanding to cover the planet. The field purifies any air, soil, water, plant life, etc within. Unfortunately, the magic is fatal to humans and the expansion is beyond the power of the Princesses to stop. A special potion is devised to transform humans into ponies, changing their bodies while preserving their minds and souls, to let them survive. This is what happens at the eponymous bureaus. In spite of technological advances, Earth is presented as an Earth That Used to Be Better, with deliberate implication by the author that some event between the present day and the fic's time left a lingering effect that causes much of humanity to essentially act smoozed. Ponification undoes this, often causing the transformed to feel very chipper.
- Oversaturated World: This is the Apocalypse How trying to be solved in the first story, as a full collision would lead to the annihilation of both universes.
- The Discworld/The Lord of the Rings Crossover fic Policing the Fellowship has Samuel Vimes accompany the Fellowship of the Ring. Over the course of the story, the fellowship characters start acting like Discworldian archetypes of themselves (Aragorn starts acting like an Upper-Class Twit - albeit still a far more competent one than most Discworld nobility, the various nobles the group encounters become much more cynical, etc.).
- On the flipside, without Vimes, the Discworld becomes more like Middle-Earth, with Captain Carrot (long-lost heir to the throne, who prefers to be a policeman) manifesting the same kind of white flame on his brow that Aragorn does, and being propositioned by three elven princesses. This is somewhat Downplayed, however, as the first one was bitten by Angua (Carrot's werewolf girlfriend), the second one's pointy ears washed off in the rain, and the third turned out to be Nobby Nobbs, who was 'just getting into the spirit of things'.
- My Little Pony: Equestria Girls Friendship Games: After Human Twilight's device absorbs the magic of the portal, it starts tearing open portals between the human world and Equestria whenever it is opened, allowing through things like jackalopes and Man-Eating Plants. When Twilight transforms into Midnight Sparkle, she starts ripping holes to Equestria to access the magic there, not caring that she's destroying her own world in the process.
- Jumanji: The flora and fauna of Jumanji that invades the "real world" is able to do things that would be impossible for real life equivalents (monkeys that can ride a motorcycle, plants that can grow incredibly quickly, a Pelican that can fly the board game without trouble etc...)
- Last Action Hero is a quasi-example. On the one hand, when an action hero crosses over from the world of movies into the real world, he nearly dies from a gun shot he'd normally shrug off as Just a Flesh Wound; similarly, a villain who makes the same leap is delighted to discover that in the real world the bad guy winning is actually possible. However, when Death crosses over into reality from the movie world, he's still able to kill people just by touching them. We also see that, when the movie hero shoots the movie villain in his cybernetic eye, it causes a ridiculously huge explosion, even when they're both in the real world. It could be said to be somewhat consistent since only supernatural or futuristic elements kept their original properties.
- The stories of H. P. Lovecraft often involve aliens that dwell in more than the traditional three dimensions and who occasionally interact with Earth. The twisting of logic and geometries involved by interacting with these alien space gods usually drives people mad as they are unable to comprehend them.
- Doctor Who Missing Adventures: In Millennial Rites, our universe gets merged with both the one that preceded it and the one that will follow it, becoming a trifold realm being slowly torn apart by its three mutually-conflicting sets of physical laws. London becomes known as the Great Kingdom, ruled by the gods the Great Intelligence (AKA Yog-Sothoth, of the Pre-Universe), Saraquazel (of the Post-Universe)... and Lady TARDIS (of... guess where). Of note: none of the three planned this, and only the Great Intelligence is at all pleased with the results.
- Isaac Asimov's The Gods Themselves is a story based around a new form of energy that arises when people discover how to exchange matter between parallel universes. The protagonist slowly realises that as they exchange matter between worlds some of the cosmological constants also change very slightly, but with potentially apocalyptic consequences.
- Rod Albright Alien Adventures: The second book in the series reveals that BKR and Smorkus Flinders were working on this, intending to create a permanent door between Dimension X (home of Reality Quakes, which periodically cause random and usually temporary shifts in reality, though the effects are sometimes permanent) and Dimension Q (where Earth exists) that would let the Reality Quakes leak over and eventually fuse them into one dimension "where reality can shift like sand" (BKR's motivation is pure nastiness, while Smorkus Flinders, who was once a normal being until a Reality Quake permanently transformed him, is doing so as a means of lashing out at the world in retaliation). However, after Smorkus Flinders is taken into captivity and BKR subsequently escapes from custody, the latter decides to focus on one of his other, older plans instead.
- In the backstory of The Witcher, the Conjunction of the Spheres was an event where a bunch of dimensions intersected at the same time and dumped several unnatural things into the world, including monsters, magic, humans in flying metal airships and elves into the world, unfortunately for the planet's original inhabitants: dwarves.
- Season five of Buffy the Vampire Slayer: the exiled Hellish God Glory is trying to re-enter its dimension, but such effort would cause all dimensions to collide (thus destroying the Multiverse). Small glimpses of this process can be seen in the final episode when places on Earth get changed and twisted and creatures from other dimensions including Cenobite-like demons and a dragon enter our realm.
- In Fringe, the space-time continuum is breaking down due to contact between the two universes, which are implied to have slightly different physical laws (the show is inconsistent on that point, though). Interesting as the bleed appears to be two-way.
- There's an episode of Star Trek: The Next Generation where aliens from another universe with very different physical laws invades the regular Star Trek universe, and start running experiments on the Enterprise crew. Somehow they manage to create some sort of temporary environment where the laws of physics allow inhabitants from both universes to co-exist, but normal parameters within that universe do pretty crazy things to people's body chemistry.
- Background material on the Nasuverse speaks of Type Mercury, the avatar of Planet Mercury, which crash landed in a South American rainforest in 5000 BC after answering Gaia's call prematurelynote . Mercury's crash site has since transformed into a "Crystal Valley" filled with beautiful yet horrifying crystal spires. This is a replication of planet Mercury's environment, and Type Mercury's mere presence has turned that patch of Earth into a patch of Mercury. It is said that its full force is activated by Type Mercury's movement, which means wherever it goes, it will leave a trail of Mercurian crystal.
- In Uzumaki, the inhabitants of a small fairly isolated town begin to notice a repeating spiral pattern that manifests in a number of disturbing ways. People, objects, plants, galaxies, space and time eventually twist into a spiral shape drawing the inhabitants in. The closing scenes show the spiral world below and the narration suggests that this spiral world invades the mundane on a regular basis, leaving only ruins behind when things return to normal.
- The Realm of Chaos in both Warhammer and Warhammer 40,000: a mirror universe with physical laws vastly different from our own. Wizards/Psykers can tap the Realm of Chaos for power, but they risk physical mutation and insanity; and if for any reason the boundaries between universes are weakened, the results are always nasty and horrifying in the extreme.
- Magic: The Gathering:
- In the Invasion storyline, the Phyrexians invaded Dominaria by merging it with an already-conquered plane called Rath. Dominaria was warped to incorporate locations and inhabitants from Rath (including the Phyrexian army), sometimes warping individual creatures or structures into hybrids combining both planes and sometimes simply dumping creatures and entire geographical features from Rath into Dominaria, such as the Skyshroud (an expansive jungle floating like a raft over the sea) getting plopped in the middle of the frozen north.
- The "Shards of Alara" block is one long example of this. Ages ago, an unknown disaster split the plane of Alara into five subplanes. Each "shard" had access to only three of the five colors of magic (each shard having one central color and its two allies), and lacked the two other colors and their associated forms of thought and behavior. Over the ages, the shards were shaped by the local limits on magic, developing into five profoundly different realms. When the shards began to merge back together, not only did the physical terrain of each shard begin to emerge in the others, but each shard had to deal with the return of colors of magic that it had not had to deal with for millennia. The arrival of philosophies and ideas people had previously found literally inconceivable shook each shard's specialized society to the core.
- Bant, the White shard, was an orderly, pastoral Arcadia of rigidly structured traditionalist societies, selfless heroism and little in the way of cultural change and flexibility. With the Conflux, Bant's rigid societies found themselves exposed to alien ideas like "treachery", "chaos" and "self-interest", while creatures, beasts and monsters from the other shards invaded the peaceful fields of Bant. In the end, this proved too much for Bant's people to adapt to, and most of the shard's civilizations collapsed under the strain.
- Esper, the Blue shard, was a City Planet whose inhabitants lived for constant progress and self-improvement, heavily augmented their bodies with metal, lived under a strict hegemony and had little use for emotion. The Conflux flooded Esper's hegemonic society with chaos and emotions the Esperites didn't know how to deal with — and the constant dragon attacks did little to help.
- Grixis, the Black shard, was a hellish wasteland where demons and necromancers ruled over a landscape of corpses and bones. It is probably the only shard that could be said to have benefited from the Conflux — the influx of Green and White mana brought life to the wastelands, while the demons and undead swarmed into the other shards to prey on their abundant and unprepared native life.
- Jund, the Red shard, was a savage, lawless Death World of dragon-ruled volcanic peaks rising above swamps and jungles full of predators and barbarians. When Blue and White mana began to enter it, the aggressiveness and natural instincts of many of its inhabitants began to simply fade away. Combined with the dragons that ruled the shard migrating away to seek new prey and targets in the rest of the world, this caused the collapse of much Jund's food chain and societies.
- Naya, the Green shard, was a vast jungle of towering trees home to human, elf and Cat Folk tribes and an endless array of creatures, all ruled by hill-sized beasts called gargantuans. While the gargantuans were able to keep most invading creatures out, the alien magic and mindsets still entered, and the Nayan jungles became infested with undeath and demonic cults.
- The WitchCraft supplement "Armagedon" is described as having elements of this in areas that are captured by the enemy, such areas are changed radically into something alien and inhospitable to normal life as we know it. Victims end up fused together in collective masses of flesh and otherwise twisted beyond all recognition.
- The game TORG is explicitly this trope, in which Earth is invaded by a number of other worlds that each have their own genre-like set of laws (which are spelled out in detail for each area, so in the pre-historic themed North America technology does not work and groups of people devolve into small tribes, whilst in the Pulp themed Middle-East people people drift into stereotypes, their allegiances become easily changeable and good triumphs over evil). The playable characters are those rare individuals who are able to carry their own native laws of physics around with them and exercise them against others.
- Shadowrun has an element of this when magic (re-)enters the world, changing the limitations of what is possible.
- Dark Conspiracy. Parts of the U.S. have been taken over by Dark Minions invading through portals from their home dimensions. These areas are known as "Demonground", and they're filled with the corruption flowing from the portals. Common elements include bizarre vegetation and weird organic tunnels.
- Witch Hunter: The Invisible World. Hellpoints are direct doorways to Hell itself. The areas around them are filled with malign influence and evil creatures. Demons may easily enter the world at these places.
- Dungeons & Dragons:
- The Far Realm, a Lovecraftian non-place outside of reality, sometimes encroaches on the Material Plane through "cerebrotic blots" — places where the laws of physics are subtly distorted. Some blots have a second layer accessed through invisible portals, which is Bigger on the Inside and far more heavily corrupted.
- Eberron has a milder example in the form of manifest zones, where traits from another plane impose themselves on the material world. While some of these are harmful, others are beneficial. The massive towers of Sharn, the world's largest city, for instance, can only support their own weight due to being built in a manifest zone to Syrania, the plane of air. Each plane also has an astrological "orbit" which can have effects on the world as a whole, such as resurrection magic acting strangely if the realm of the dead is too near or too far.
- The setting's most notable example is the Worldwound, an enormous Hell Gate to the Abyss that swallowed most of a nation. Besides being filled with demons, the influence of numerous demon lords and the Abyss itself have twisted the surrounding land into something horrible. The remaining plants and animals are either undead or horribly mutated, the land is barren, blasted and wracked by earthquakes and geysers of filthy water, most lakes and rivers have drained into rifts to the Abyss, the sky is tinted in strange colors, snow and rain are oily and foul or replaced by insects, blood or worse, and in the most corrupted places even the sun, stars and moon don't look or move like they should.
- This happens in the second and fifth installments of the Reign of Winter adventure path, both times due to overlaps of the First World, the strange and chaotic world of the fairies and an alien and supernatural place even by the standards of the regular High Fantasy setting, with the material world.
- In The Shackled Hut, Queen Elvanna of Irrisen captures Baba Yaga's dancing hut and chains it on display in her capital's market square. The hut defends itself by forcing a breach to the First World, causing an impassably thick forest of conifers, which grow back as fast as they're cut down, to grow overnight in the square and spread for several blocks before being stopped. The result is a patch of The Lost Woods sitting incongruously in the middle of a large city's merchant district, filled with a mix of stranded locals and of First World beasts and natives that found themselves dragged into the material world alongside the forest.
- Later, Rasputin the Mad Monk combines magic and Nikola Tesla's technology to bridge the two worlds and take over the Thrice-Tenth Kingdom, Baba Yaga's First World domain. The machinery used to breach the fabric of reality and the overlap with the First World severely affect the area around the Siberian monastery where Rasputin is hiding — the landscape becomes a fusion of those of Earth and the First World, and the monastery itself fluctuates between its actual ruined state and a beautiful, lighted and restored version of itself as the worlds overlap and move apart. Meanwhile, the arcane energies washing across the land have animated trees and clouds of mustard gas to malevolent life and allowed slain Cossacks to rise as undead dullahans — things normally quite impossible in magic-poor Earth.
- Corpse Party takes this trope to extreme lengths. The protagonists are trapped in what are mentioned "closed spaces layered over closed spaces." In each chapter, the main characters you play as are all in the same school but a different rendition of it, with events taking place before or after each other that seep into the others' dimensions. Best example is how Ayumi leaves candles for others that act as a Save Point after she and Yoshiki look for Seiko when she screams... yet when you play as Naomi and Seiko in Chapter 1, the candles were already there.
- In The Longest Journey, the technological world of Stark and the magical Arcadia are usually well-insulated from each other. However, when the Balance between them begins to falter in the beginning of the game, weird stuff begins to happen in both worlds, such as a TV show about rainforests transporting the viewers into an actual rainforest, or a handheld calculator trapping a mage tampering with it inside.
- Wild Arms 2: The source of most of the plot's conflict is an "encroaching Alternate Universe". The only way to fight this is through a LOT of magic and plot twists that temporarily give it physical form.
- Shadow Warrior 2 sees the Shadow Realm merging with the human world as a result of Lo Wang's actions in the first game, with the wildlands constantly changing, creating a strange and savage new order where humans and demons live side by side.
- The Legend of Zelda: Twilight Princess: The Encroachment of the Twilight Realm upon Hyrule, which fills the region with terrifying beasts, many of them former natives and wildlife of the land corrupted into monstrous forms by the Twilight, and turns humans and hylians into spirits (and in Link's case, a wolf). Unlike most Dark Worlds seen in the Zelda series, very little of the Twilight Realm itself is seen except when overlaid onto Hyrule.
- Puyo Puyo Tetris: The Excuse Plot for Story Mode is that the worlds of Puyo Puyo and Tetris are colliding for some reason, causing Primp Town to be covered in Tetriminoes and Tee's spaceship to be flooded with Puyos.
- Gravity Falls: According to the Author of the Journals, Bill Cipher has been planning to merge the Nightmare Realm with the physical world in order to turn it into a nightmarish World of Chaos for him and the rest of the dream demons to invade and rule as their personal playground. After Bill successfully unleashes Weirdmageddon upon Gravity Falls in the finale, Dipper must find and rally his allies to fight back and liberate the town before Bill can spread his influence throughout the entire universe.
- The Real Ghostbusters:
- In "Knock, Knock", after opening a doorway that was supposed to remain closed until Doomsday, the ghost world starts entering our plane and turning things into monstrous versions of themselves (for example, trains into worm-like monsters). This was intended to be what would happen to the world After the End.
- In "You Can't Teach an Old Demon New Tricks", after traveling to a demonic dimension through a magician's cabinet (and finding dozens of beautiful assistants and doves) the ghostbusters meet a demon obsessed with becoming a magicians. He agrees to let them back to their home dimension if Ray teaches him magic. Unfortunately, after Peter opens the doorway, both dimensions start mixing and New York starts turning into the demons hellish dimension.