Type 3 or Out-universe links are all those reference that imply any kind of relationship between two series, while not being actually linked within their universes. It's called "out-universe" because the link only happens in the real world, not within the fictional universes.
Every reference in a series to another series, if it doesn't imply anything from the referenced series to also exist in the referencing series.
Appearances in a series of elements only similar to those from another series.
Two series sharing some history together such as being released together in a boundle or both being part of notable events.
A type 3 link is directional when it's a series to reference the other one. This may be any kind of intentional similarity between the two series, or any minor reference.
A type 3 link is undirectional when the two series are linked from sharing some history. This may be being released together in a boundle or both being part of notable events at the same time.
Type 3 spinoffs
A Spin-off series is of type 3 when the spin-off only takes stylistic elements from the parent series and uses them as defining elements in its own. This often corresponds to the spin-off being considered a "spiritual successor" to the original series.
Main article: Type 2.5 link
Type 2.5 links happens when a series uses elements similar to ones from another series to make them fictional in its own. This is considered a particular type 3 link since in fact it's still a just a minor reference between the two series, but it might be notable distinguishing them sometimes.
When talking about links in general in this Wiki, type 2.5 links are considered the same as type 3 links, unless specified otherwise.
See also: Links in Crossover Wiki pages
In this Wiki type 3 links are treated like any other link type, but specifically:
Type 3 links are indicated in italic when graphically representing them. For example:
indicates a directional type 3 link from Series A to Series B.
The explanation images used in link pages are:
Series A Series B Directional type 3 link: the arrow indicates that an element from Series A, represented as a yellow smiling face, was referenced in Series B, while not actually appearing it, with the reference being represented as a green face, which is a modified version of the original one.
Series A Series B Type 3 spin-off: The big arrow indicates that the whole Series B exists as a spawn of Series A, but it only features elements inspired from the ones in that series, and this is represented by the green face, that is a modified version of the yellow face.