When a superhero comes across a mystery in a comic book, it usually becomes the focus of their adventure, and by the end of the book (or arc), that mystery is solved. That makes sense, and it's pretty much how storytelling works, but every so often, a mystery comes along that even Batman himself has trouble solving.
Granted, it's rare, and there's a good reason for that. Batman wouldn't be the World's Greatest Detective if he got stumped every other issue. Even though he's good at his job, he's dropped the ball on sleuthing a few things over the years, and he's not the only one.
Over in Marvel, Image, and numerous other universes, there are superheroes who have had to scratch their heads and admit there are just some mysteries that can't be solved by the end of a comic book. When it happens, the fans tend to speculate, but even the Internet can't answer everything.
There actually aren't all that many mysteries superheroes had trouble solving given the length of time their books have been out, but there are at least ten. The ones featured here are either the hardest ones to solve, or they remain a mystery because the writers and artists simply haven't given anyone the answer. At least not yet...
10. The Joker's True Identity
This is a big one, and it's the one most people think of when it comes to unsolved mysteries because the Joker's true identity has never been confirmed. There have been hints and various allusions over the years, and he's definitely been expanded on in television shows and films, but in the world of comics, it's far more confusing.
The Joker has been around since the beginning, having first appeared in Batman #1 in 1940. You would think his name might have been dropped sometime in the intervening eight decades, but it hasn't, and recently, his identity has gotten even stranger.
In 2016's DC Universe: Rebirth, the longtime publisher dropped a bomb in terms of the Joker, and the fans are still trying to get over it. The one-shot confirmed that there are, in fact, three different men who have the same identity as the Clown Prince of Crime in Gotham City!
The story didn't give the readers much more information than that, but Geoff Johns and Jason Fabok have confirmed that the forthcoming Batman: The Three Jokers will clear everything up. That being said, there's no indication it will clear up the true identity of the man who has plagued Batman for the better part of a century.