Obvious Crossover Method
A Fandom Specific Plot Crossover Opportunity
A specific species of Fandom-Specific Plot, an Obvious Crossover Method is any method or episode that has sufficiently obvious crossover possibilities that it is regularly used to set up crossovers. Before adding an example, think if the method has been used frequently enough to qualify as a Fandom-Specific Plot; if it doesn't, it doesn't go here. Compare Sailor Earth (a Sister Trope of a gap in the setting that can be filled with an OC, a minor character, or, overlapping with this, a crossover character), The Stations of the Canon (which is more about the effect; this is about a possible cause). Examples:
- The Springtime Summoning Ritual in Familiar Of Zero
- Buffy the Vampire Slayer has at least three:
- The second season Halloween episode, aka YAHF.
- Buffy jumping through a portal at the end of the fifth season.
- The "Slayer Speculation Fic", where a crossover female character gets Called as the Slayer.
- Kingdom Hearts as a whole, given the nature of its cosmology.
- The Nanban Mirror (filler) from Ranma ½ allows time-travel crossovers.
- Also common: Ryouga wanders into another series.
- The sliding device from Sliders.
- Fringe has alternate world travel in the later sesaons.
- Stargate as well.
- Total Drama Island has 'what if [teenage character from another franchise] was a contestant?'
- Touhou's Yukari Yakumo has been known to "spirit away" unsuspecting individuals from outside who she takes an interest in and take them to Gensokyo.
- Since Doctor Who can theoretically take place anywhere in time and space, it's pretty easy for it to have crossovers with anything just by having the TARDIS land there. Even in cases where the other work's universe conflicts with that of Doctor Who, there are rare occasions in which the TARDIS travels to other universes.
- A crossover character is the one who raises Harry Potter.
- A crossover character winds up in Harry Potter's first year.
- Malfunctioning Stargates from, well, Star Gate.
- The Gate from the 2003 Fullmetal Alchemist anime. We know it leads to one parallel universe, so why not another?
- For Western Animation in general, using the Toontown concept from Who Framed Roger Rabbit.
- The malfunctioned slipspace portal at the end of Halo 3.
- The Endless concept from Sandman qualifies; given the nature of the cosmology in that plot, literally every universe ever imagined has existed, and the Endless represent fundamental concepts such as Death, Desire, Dreams, and Destiny. Usually the crossover is a brief encounter between a character and either Death or Dream, in that order of probability.
- Mortal Kombat's mythos holds that "your world is but one of many realms", allowing the title tournament to be held in pretty much any world.
- The world of Rifts was practically built for crossovers -- one never knows where a Rift might lead.
- Kamen Rider Decade is walking crossover bait. Hell, he's responsible for the first ever Super Sentai / Kamen Rider crossover.
Hello, Unknown Troper. You'll need to get known to lend a hand here.