Entertainment journalist James Grebey defined fan theory as “ideas and speculation that audiences have about movies, shows, comics, or anything.” He believes they exist because fans are passionate and creative about the things they love.

There are several types of fan theories that are distinguished by the different goals they try to achieve. The mystery-solving theories, for example, attempt to figure out an enigma that actually exists in the work of fiction. 

A lot of these theories are eventually confirmed by filmmakers. Like Harry Potter being Voldemort’s Horcrux. Before the entire release of the Harry Potter series, viewers and readers were able to put the puzzle together and solve it. In the final part of the book Harry Potter and the Deathly Hallows, such predictions were confirmed, much to the audience's delight.

Another type of theory is a predictive one that essentially poses the question, “What happens next?” Avid film viewers try to pick on various details and hints that allow them to speculate what may come next in the story. This is essentially called foreshadowing and generates quite elaborate and interesting theories.

The plot-hole-filling type of theory tries to answer questions that aren’t as important. Since continuity errors happen in movies and TV shows, people attempt at explaining them—not always successfully though. One of the most famous ones is pondering whether there was enough room for Jack on the door in Titanic.

The following two, retcon and head-canon theories, are already treading the absurd category. The former one tries to argue that what you saw on the screen didn’t actually happen, like Black Widow not actually dying in the Endgame. These speculations rarely make sense, as disproving something we can see is almost impossible. 

The head-canon theory is fun, usually used to creatively engage fandoms. Just like the idea that Elsa and Anna from Frozen share the same parents with Tarzan. Such claims usually don’t have substantial reasoning behind them and often annoyingly spam movie watchers. However, it might be worth mentioning that the theory that Peter Parker made an appearance in Iron Man 2 was just a head-canon at first that Marvel made to come true.

The final theory is a real-life one, and as the name suggests, it speculates about the real world. For instance, how Dsiney or Sony will handle licensing disputes. This, of course, can be a lot of fun for fandoms but the issue with them is that some reporters portray them as truth in their articles and deceive their readers.

To wrap things up, I’ll leave you with one more fan theory that might seem unbelievable but turned out to be actually true. After Robocop came out in 1987, viewers were quick to point out that the story weirdly resembles the one of Jesus Christ: the man is killed and then resurrected to save humanity. The theory was confirmed by its director, Paul Verhoeven, who said that it’s of course a Christ story. “It is about a guy that gets crucified after 50 minutes, then is resurrected in the next 50 minutes and then is like the super-cop of the world,” he added.