List of crossovers in video games

Crossovers in video games occur when otherwise separated fictional characters, stories, settings, universes or media in a video game meet and interact with each other. These may exist as a gimmick if two separate games in question are developed by the same company. Otherwise, they may exist as a gag from a rival company.
The following is a list of games in which crossovers appear in either the form of a cameo of any kind, a guest character, or the theme of "crossover" in general in a video game itself.
First and second-party crossovers.
This list includes crossovers and cameos of characters from video games owned by one company and close affiliates. These can range from a character simply appearing as a playable character or boss in the game, as a special guest character, or a major crossover where two or more franchises encounter.
Third-party crossovers.
This list includes video games that have crossovers from two or more separate companies.
Comic book/video game crossovers.
Video games that have comic book franchise characters encountering or facing off against other comic book franchise characters or third-party video game characters in a crossover video game or as a guest character in a third-party video game include:
Cartoon/video game crossovers.
Video games that have cartoon franchise characters encountering or facing off against other cartoon franchise characters or video game characters in a crossover video game or as a guest character in a third-party video game include:
Manga/anime crossovers.
Video games that have manga franchise characters or anime franchise characters encountering or facing off against other manga or anime franchise characters in a crossover video game include:
Scrapped crossovers.
These crossovers were planned during development, but were removed from the final product: