Any specialised wiki, as it continues to grow, will tend to accumulate general, more encyclopedic, information.
For every wiki out there that exists by The Wiki Rule there is the issue of some additional knowledge not exactly under the main mission of the site still being very useful for understanding the behaviour of the site's focus. There's also the fact that the internet exists globally while a wiki's contributors can exhibit local variations in behaviour and these often have to be explained.
For example, our Useful Notes pages exist to help people understand things that may be taken for granted under the Creator Provincialism of other contributors or of TV writers. It started with issues of geography and then extended to subjects that have a complex relationship with their portrayal in media. Things which it is useful to know in order to understand everything that is written hence Useful Notes. Even before this, we also have pages on production trivia and audience reactions, which are not in fact tropes by themselves but which still impact on how stories are written such as Executive Meddling and the Fandom tropes.
This effect dates back to the original wiki, Ward Cunningham's Wiki Wiki Web. There were enough Separated by a Common Language problems that users felt the need to create a page explaining "American Cultural Assumptions"... which turned out to be similar to our Useful Notes pages.
- Halopedia, the Halo wiki, has a page on corn, as well as other things, due to it being an inclusive wiki.
- The Transformers Wiki has a lot of information on toy production and technology. The Transformers Wiki also has pages for Jesus (probably existing to service the comparisons between Optimus Prime and Him) and Michael Jackson. Hilariously, it pointedly does not include any information that does not show up directly in Transformers-related media, even if it would be relevant general knowledge otherwise.
- Wookiepedia, the Star Wars wiki, includes pages on gender and death, among other things. It even an article on breasts, which has caused quite a bit of problems when outside forces came to the site's community complaining about it.
- This Very Wiki used to stick to television, hence the name. Now it covers tropes from all conceivable media, and some things that aren't technically tropes at all.
- Since Donkey Kong exists in the same universe as Super Mario Bros., it isn't surprising that the Super Mario Wiki would have some information on the DK characters and games. However, it has extensive information on everything Donkey Kong-related, even more than the actual Donkey Kong wiki. The wiki even has pages for characters in series such as The Legend of Zelda, Metroid, Fire Emblem, and many others due to their inclusion in Super Smash Bros., which the wiki kinda treats as a sort of Mario subseries/spinoff.
- The Harry Potter Wiki has several articles like this for anything mentioned or shown in Harry Potter, including the Game Boy, Electricity, and Stephen Hawking.
- The Doom Wiki, which gives an equal regards to the narrative, historical and technical aspects of the Doom series, also completely documents the narratively seperate Heretic, Hexen and Strife, all of which were programmed on the original Doom engine, as well as any notable Doom Game Mod. It also has brief pages on Wolfenstein 3D, the original Rise of the Triad, Quake I, Shadowcaster and Raptor: Call of the Shadows, who all have a technical history involving the Doom engine, as well as briefer pages on Dueling Games Duke Nukem 3D and Marathon. It does not, however, covers Hexen II and Heretic II, which were programmed on Quake series engines, nor does it covers any game programmed on Doom 3's id Tech 4 engine beyond Doom 3 itself.
- Wikizilla is the Godzilla wiki, but it also describes the Gamera and non-King Kong vs. Godzilla/MonsterVerse King Kong movies in the same depth, and even has entries on a number of completely unrelated kaiju movies.