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?