This is a pretty simple question, but an intriguing one that I think about all the time. Sometimes, when I’m watching a movie or reading a book, I always notice some similarities to other things that I have watched or read. I then begin to realize that there are a lot of questions that could be answered if these seemingly unrelated universes were connected.
So, I ask you this: do you have any headcanons of connected fictional universes? and if so, what are they?
G1 and G2 being connected, it’s kinda cannon, but not fully. Changed category to Entertainment ~ TheMOCingbird.
Well I always believed that Hero Factory is in the same universe with G1, and Mr. Makuro is a Turaga.
I’ve thought about that, too.
I also have no idea why, but I really believe that the movies You don’t mess with the Zohan and The Dictator are in the same universe.
I feel like some aspects of hitchhikers guide to the galaxy and guardians of the galaxy could be in the same universe
Smash Bros headcanons are my thing.
I imagine Ridley being good friends with Pichu due to one adorable twitter comic I saw.
I sometimes just imagine the X-Men movies, Deadpool movies and MCU Movies in the same universe
I also believe Simpsons and Futurama
Everything Wes Anderson has ever made
Everything Quentin Tarantino has ever made
Transformers and G.I. Joe
Gravity Falls and Rick and Morty.
This is weird but I imagine all the RP’s in the same universe
(I blame @Mctoran, when he connected RP’s, I made connections)
I kind of like the idea of Overlord (2018 WWII zombie / horror movie), being set in the Machine games Wolfenstein universe.
Also I like to think about how all biopics take place in the same cinematic universe - just with incredibly inconsistent casting and occasional continuity errors.
What’s a biopic?
Biopics are films about real people - essentially a biography in film form, except usually less comprehensive because trying to cram a persons entire life into a single film is a silly idea (though many have tried). Examples would be The Kings Speech, Bohemian Rhapsody and The Social Network 
Lincoln is my favorite
The Invasion and Big In Japan
OK, so, here is a theory that makes too much sense to be fake.
Independence Day in Star Wars.
Think about this: after the humans destroyed the aliens, they got the taste of it. They start developing space technology out of various reason. Space race to the moon? I say space race to Mars, or Saturn, or Pluto! After the brake-up of the Soviet Union, Czechoslovakia and Yugoslavia, all of the European states start working together to make their own space agencies to protect their people. I am talking about a Northern American agency, a German agency, a Balkan agency, so one so fort.
After Earth becomes inhospitable they go on and colonise new planets: Alderaan, Tatooine, etc.
And so, after millennia of colonisation and living in peace with the local species, we get the Prequels.
Also, about Independence Day: I don’t care, I know I’m sadistic, there was totally a shipwreck at the entrance in Bucharest. Come on! There were more than 8 of those! You can’t tell me that Bucharest was not a target!
HF and Bio G1. I actually have a half formed Fan-fic/storyline/rough concept called a Clash of Two Galaxies based on it. Hate me if you wish.
(and Mr. Makuro is definitely a turaga)
Hear me out, Minecraft and Isekai Quartet.
I think that if we saw the crew, from Isekai Quartet, transported into Minecraft’s world, that it would be a unique and hilarious show.
Not too mention seeing all of them meet their first creeper would be pretty funny. I have to wonder what Ains’ reaction would be. Tanya would probably and somehow scare the creeper.
I think at least Ainz would know what a creeper was from his life before being isekai’ed.
Very true, however we don’t even know if Ains had Minecraft in his Earth.