Type 1 links or in-universe links are a type of link that happen when elements from two series interact with each other in an actual physical way, within their fictional universes. They may be directional, with elements from a series appearing within another series, or undirectional, with the two series meeting in a crossover. In both cases elements from a series appear as real for the other series, the two physically meet in their fictional universe, making this the stronger and most notable type of link between series. In-universe links are ofter called "crossover", but technically the crossover is a work created pureposelly to tie two or more series, so not all kinds of cameos and references should be called crossovers.
Everytime elements from a series are considered "real" for another series' universe, specifically:
- Something from a series being implied to also exist in another series, such as:
- A character from a series making an appearance in another series. (No matter how relevant the appearance is, it might be a regular guest appearance or a background cameo)
- A place from a series being featured in another series.
- Elements or events from a series being mentioned in another series, as long as they are implied to be real and not fictional within that series.
- Two series meeting in a direct crossover. (not counting format crossovers)
- Two series being revealed to take place in the same universe or in general sharing some elements from official sources even outside the series themselves.
Appearances of elements only similar to those from another series, while not being actually them.
Appearances of elements from another series without being officially licensed.
Appearances or mentions of elements from another series without being implied to be real, and therefore only being fictional within the series.
Directional in-universe links happen when an element from a series appear as a real element within another series. The most common example of type 1 link is a character from a series making a cameo appearance in another series, but it may be anything instead of a character. For example it may be a weapon, such as a video game series featuring a secret weapon from another game series, or an organization, as it sometimes happens in books and TV series, or even a fictional work within the series, such as a book within a movie also appearing in another movie. The link may also happen purely in a sentence, like characters from a series saying that they went on holiday in a specific country that was previously featured in another series. Basically every time something from a series is revealed to also exist in another series, a directional type 1 link happens.
The strict requirement for the reference or cameo to be considered in-universe is that the element has to be featured as something real in the other series. Puppets of characters from other series, toys of weapons from other series, posters of scenes from other series don't prove that anything from that series exists in the other series more than it does in the real world, and are only considered sub-universe links.
A particular case is that of clothing (see Link#Clothing). If clothes from a series appear in another series, that is only considered an in-universe link if those have specific features other than the appearance, to make them identify as the actual clothes and not reproductions. For example, clothes from the Assassin's Creed series have appeared in Metal Gear games and vice versa (see Assassin's Creed X Metal Gear), but that doesn't necessarly means that anything from either series really exists in the other, since clothes based on video game series also exist in the real world. However if the Metal Gear uniform in Assassin's Creed was, for example, the OctoCamo capable of changing its texture and retained its special feature, then it'd be considered the actual suit from the other series and create an in-universe link.
Type 1 spin-off
In-universe spin-offs are the most commonly recognised type of spin-offs and include all series featuring elements from another series as defining elements. The most common type of in-universe spin-off is a series starring a character from another one as the main character, that may either be a secondary character, a villain or even the protagonist of the original series. A series is also always considered a spin-off if its named after a character or any element from another series, but may also be considered a spin-off if it has enough supporting characters from another series, even if featuring original protagonists.
Sometimes a series featuring characters from another one, or being set in the same fictional universe isn't considered a spin-off, because the references only happen as secondary features and are not defining of the series, making them regular directional in-universe links. In some cases it might be difficult to decide if cameos are or not defining elements of the second series, but most times we follow how the creators originally intended the series: if they either wanted it to feel like a separate thing, only with some references to the original series, or if they wanted it to feel like a continuation. If there isn't any official statement regarding this, we usually just follow how the series is usually felt by the audience.
Spin-off series, being separate series from the parent one, can still have additional type 1 links to it, such as a character that originated in the spin-off appearing in the parent series, but even a character from the parent series appearing in the spin-off may be considered a separate link. An example is the Mario series, that's a spin-off of the Donkey Kong series since it stars the same main character from the first Donkey Kong game, but the first Mario games had very few elements from Donkey Kong games, so the appearance of Donkey Kong Jr. in Super Mario Kart is a notable cameo that creates a Type 1 link directed toward the spin-off series.
For the most part undirectional in-universe links are identified as direct crossovers, that are defined as:
A direct crossover is a fictional work that's part of two or more series.
It shouldn't be confused with crossover series, that's a work featuring elements from other series as a prominent feature while not necessarily being part of them.
An example of direct crossover is the Mario & Sonic series of games, that's part of both the Mario and the Sonic series, so it's considered a crossover. An example or crossover between more than two series is the Aliens versus Predator versus The Terminator comic, being part of the Alien, Predator and Terminator series.
Direct crossovers create an undirectional link because there's no element going from a series to the other, but they simply coexist together. It's obviously an in-universe link because elements from the two series meet each other, but there may be exceptions of crossovers only featuring elements from a single series. An example is the videogame Dance Dance Revolution Winx Club, that's part of both the Dance Dance Revolution series and the Winx Club series, thus being considered an in-universe crossover between the two despite it only featuring in-universe characters and places from the Winx Club series and no element original from the Dance Dance Revolution, therefore basically just being a Winx Club game with gameplay from the Dance Dance Revolution games. It is so because being a Dance Dance Revolution game, it's still considered part of its multiverse, and the characters appearing in it are actual Dance Dance Revolution characters once the game is titled "Dance Dance Revolution", so the two series actually meet in-universe because at some point, one of their universes coincide.
Note that an implied requirement for a work to be an in-universe crossover is that it has to be one single work. Sometimes two or more works from different series are created as a single episodic work and released together, maybe even marketed as a crossover, but in these cases, even if they feature a single title, they're considered different works from different series, just boundled together, only creating an out-universe link. An example is the movie Mario Kirby Meisaku Video (unofficially translated to Mario Kirby Masterpiece), that's listed in both the Mario and Kirby series, but it's not considered an actual crossover between them because it actually features two separate movies with Mario and Kirby not interacting in any way.
Another exception is the format crossover, that's an entry in two series, but only features stoyline elements from one of them and some format from the other series. This is only considered a type 3 link.
Such boundled releases, being considered separate works can paradoxically interact with additional type 1 links. It might happen that in a release of two or more fictional works boundled together, its included series occasionally interact. An example is the Heathcliff and The Catillac Cats TV series, that boundles together the Heathcliff TV series and the Catillac Cats TV series, but the two of them also shortly interact in the show's closing credits, where Riff-Raff from Catillac Cats is shown taking his hat back from Heathcliff. In that case the show is still generally considered to only be a boundle, but it also features an additional type 1 link between the two series. In this example the additional link is ecceptionally undirectional since it happens outside both series, but such cases may also feature regular directional type 1 links, such as characters from Catillac Cats making a cameo appearance in a Heathcliff episode, while still keeping the two works separate from each other. Note that the simple appearance of characters from both series together on the cover (as happens in Mario Kirby Masterpiece) is not considered a fictional link, but rather a commmercial image and is not notable unless a specific illustration of characters from both works interacting is created.
Apart from direct crossovers, undirectional links between two series may happen outside the involved series, therefore being Undirect links. This happens when elements from two series interact within a third series, but in most cases these type of links are not notable, being instead implied from the direct link between the two series and the third one. An example is two characters meeting in a third crossover series, but the direct link of the third series taking characters from the other two implies that the two may interact with each other as any character in the series do, so it's not notable.
Links between two series happening in another series are only notable if the direct links between each of the two series and the third series are of less relevance. An example is when the elements from the two series meet within a fictional work within the third series, such as in the case of the "Star Fox" microgame in the game WarioWare: Smooth Moves that while being based on the game Star Fox, features a giant R.O.B. robot as a boss, thus creating an undirect link between the Star Fox and the Famicom Robot series (see Famicom Robot X Star Fox#WarioWare: Smooth Moves). Microgames are supposed to be videogames within Wario's universe, so this means that Star Fox and R.O.B. are both fictional within his universe, creating a direct sub-universe link, but the resulting undirect link is in-universe, because R.O.B. appears as a living robot within this version of Star Fox's universe, so it's notable.
Another kind of undirect in-universe link may happen outside any series, in official statements or non-fictional works such as strategy guides or encyclopedic publications, revealing that at some point the two series met. A common example is an author revealing his stories to take place in the same fictional universe, even if not connected in any other way. These kind of statements are notable as long as they connect the series more than direct links do. If the two series were already directly linked, the official statement is not notable, and is considered to only come as a confirmation to something already implied by the direct link. In case the statement gives notable additional informations it's still not considered a link on its own, but rather streghtening the existing link, so these informations should instead only implemented in the direct link's canonicity examination (see below).
As said before, In-universe links can only be considered as such if something from a series is real for the other series, but for it to be real it's necessary that it's the actual element and not an imitation. If a series features a cameo of a character looking similar to one from another series, but not the same, then in most cases it can't be considered as the actual one, but rather just a character based on it, making this an out-universe link.
The first requirement for an element to be considered the actual one from the other series is the authorization from that element's copyright owner. Other sites sometimes list cameos as actual even if not authorized, but that's only right from the viewer's perspective, since there might be no visual difference, however since we're talking about in-universe links, we want to examinate the references from the fictional universe's perspective, and in that case only the actual owner of a fictional series, or other companies authorized by them, have the right to use the actual elements of a series, therefore making any unauthorized cameo only an out-universe link. If for example a series features the cameo of a character looking exactly as the one from another series, and maybe even named the same, if they have no right over that character, than that's actually just a character looking like the original one, but not actually it.
On the other other hand an authorized cameo is considered actual even if the element appearing has significant differences, because if officially authorized, it's considered an actual istance of the element anyway. The fact that that element has different features than it usually has only concern the link's canonicity examination (see below).
Usually the defining element for an element appearance in another series to be considered actual is the name, because, even if it's an authorized cameo, if the element is named differently, than it's not the original one, but another one based on it, making the cameo an out-universe link. In case the element is not named (either because it had no name in the first place or it is not named in the cameo) than it's assumed to be the actual element, if the cameo is authorized.
As said before, in the case of clothing, even if it's authorized, a character wearing the same clothes as one from another series, it's considered a sub-universe link.
In fiction it's considered canon to a series every work that's recognized to take place in the same continuity. In the case of in-universe links, they are sometimes recognized to be canon to only one of the two series, both of them, or none of them. Theorically a canon link should be more relevant than an uncanon one, however in this wiki we consider them equal, since every series usually has different continuities anyway, so even if a crossover happens outside any previously enstablished continuity, it's an official continuity just like the original ones, and also because recognizing a crossover as canon or uncanon often requires deep knowledge of the involved series, and the result is arguable anyway.
When possible, despite it not influencing a link's relevance, the canoniy of it should always be specified in the link's description. Its canonicity is most times indicated in official statements, but when it's not, it can be found analyzing the link to see if it could or couldn't take place in each series' continuities, and what are the implications in case it does (such as revealing that part of the events of a series were canonically always infuenced by another series, but also pointing out inconsistancies between the series and the crossover in case they're confirmed to take place in the same continuity).