This article is a list of miscellaneous characters that are have made minor appearances or mentions in crossover media. The characters in these lists are part of one of these categories:
- The character has only appeared in an unofficial crossover that had their owner involved, such as an already established character appearing as a playable character in a fangame or a mod. An example would be Adelaida in the fangame Sonic Smackdown by ArcForged. While the game is not an official project by Sega, the owners of the Sonic the Hedgehog franchise, Adelaida originates from the video game Origin of Storms, which was developed and published by Sonic Smackdown creators ArcForged.
- The character is mentioned by another character, but does not make an appearance in a crossover. An example would be Jon's Mum being mentioned by Jon in Jerry Jackson's FM.
- A character's only crossover appearance is a small cameo appearance in one specific scene. An example would be the Agent's cameo appearance on a poster on the Nevada stage in Newgrounds Rumble.
Each list is split into different companies, listed below.