Many superheroes have maintained secret identities from the public over the years, but there are a few whose true identities have been hidden even from readers, usually as a way to build suspense and immersion alongside the other characters who are struggling to make sense of the secret at hand.
Right now, DC is brewing up a new version of that same mystery with Boy Thunder, Superman's long-lost sidekick from the past who is secretly someone DC readers "have known for decades."
Meanwhile, in the MCU, Harrison Ford is reportedly taking up the role of General Thaddeus 'Thunderbolt' Ross for Captain America: New World Order, raising speculation that he'll become a version of the Red Hulk, whose true identity was hidden from readers for years.
And that's saying nothing of the question of who may be a Skrull in Disney Plus' Secret Invasion streaming series…
Here are our picks for the ten most notable examples of superheroes and villains whose identities were hidden from readers.
The current ongoing volume of Savage Avengers (one of Newsarama's picks for the best graphic novels to read this fall) features a team of time-tossed Avengers who were thrown into the distant past in a fight with a Deathlok from the future.
For the uninitiated, a Deathlok is a kind of killer cyborg made from the tissue of dead soldiers - kind of Marvel's RoboCop-before-RoboCop. In Savage Avengers, the Deathlok has a secret identity, a known Marvel hero whose corpse provides the base for the deadly assassin.
And that hero is none other than Miles Morales.
We'll save all the twists around how future Miles becomes a Deathlok, but as with many of the entries to come, the story is seeded with clues and hints about who's under the steely faceplate of Deathlok, and when the reveal hits, it hits big.
Wally West was the Flash through pretty much the entire '90s. But for a brief moment, Walter West was the Flash.
When Wally disappeared into the Speed Force, a different Flash with a dark red and silver costume - and a much darker personality to match - emerged.
As it turns out, this was actually a different Wally from a different timeline, who went by his full name and had a much more mature and angry personality as well.
Wally West eventually made it back home after a short time, but the saga of his replacement by a different, alternate version of himself was only starting (a complex tale for another time).
Speaking of '90s members of the Justice League, around the time of the original Death of Superman (so, exactly 30 years ago this year), the League had a mysterious member named Bloodwynd who possessed magical abilities.
The full explanation behind Bloodwynd is… a lot. But the TL:DR is that he was actually Martian Manhunter in disguise, though there was also an actual Bloodwynd who he was temporarily replacing.
Bloodwynd may be a strange footnote in '90s DC history, but for fans of that era, he remains a cult favorite.
On that note, in the early '00s, Marvel pulled a similar trick with the New Avengers, adding an enigmatic ninja named Ronin to the team.
The mystery of Ronin's true identity was built up, but speculation that it was Daredevil eventually spoiled the intended reveal.
Instead of Daredevil, Ronin's secret identity pivoted to being Echo, one of Daredevil's allies who remains an Avenger to this day.
As for the Ronin identity, it was eventually passed on from Echo to Hawkeye, who is the other hero most associated with the identity - though a later volume of Mighty Avengers briefly had a mystery Ronin who turned out to be Blade, also still a current Avenger.
DC's early '00s year-long weekly comic 52 had its share of mysteries, but for fans who got hooked on reading the story as it was releasing (including yours truly), one of its biggest questions was the true identity of the enigmatic hero Supernova, who popped up in Metropolis while Superman wasn't around.
Supernova's secret identity was a hot topic among fans, many of whom held fast to their belief that he was actually Ted Kord/the Blue Beetle, who had died not long before the start of 52.
But in actuality, Supernova was Ted's best pal, Booster Gold, who had been front-and-center all along. This was also a fan theory, but some considered it unlikely as Booster and Supernova had come face to face.
As it turns out, that's cause Supernova was a second version of Booster from the future who was in disguise to preserve the timeline. He and the present-day Booster's timelines converged at the end of the story, leaving just a single Booster intact.
Red Hulk and Red She-Hulk
We mentioned Red Hulk at the top, and there's a good reason he cracks the top five on our list of heroes and villains whose identities were hidden from readers.
Red Hulk was introduced in the wake of 2007's World War Hulk, and though readers knew his origins as a Hulk created by MODOK and the Leader, the human behind the Hulk was a major story secret for two years until it was revealed in 2010's World War Hulks (a sequel to the original) that Red Hulk was actually Bruce Banner's longtime enemy General Thaddeus 'Thunderbolt' Ross.
What's more, this entry's a bit of a two-for-one, as the mystery of the Red Hulk was accompanied by the mystery of the Red She-Hulk, who was eventually revealed as Thunderbolt Ross' daughter Betty Ross.
Thor: Love and Thunder made no secret that Jane Foster was its new wielder of Mjolnir as the Mighty Thor, even to Thor Odinson himself. But in comics, neither readers nor Odinson knew who the Mighty Thor really was for some time.
Sure, there were plenty of hints, and everyone had their favorite theory as one might expect, but the final reveal of the new Mighty Thor as Jane Foster still came as a shock (pun intended).
Nowadays, it's hard to separate the idea of Jane Foster from the Mighty Thor, but back in 2014 when she first picked up the hammer, the identity of Mjolnir's new wielder was a big question.
For those in the know about DC villain Monarch, please rest assured we're not saying it's a good story or a great character - but Monarch and the rigamarole around the reveal of his secret identity are a notable and well-remembered (if also highly disdained) part of DC history.
That preamble out of the way, for those who weren't around to be disappointed by comic events in the early '90s, Monarch was the villain of the DC story Armageddon 2001.
The plot of Armageddon 2001 flashed between a present-day cast of heroes and the future year of 2001 which was ruled by the armored dictator Monarch - who was actually one of the story's present-day superheroes in disguise - setting up a big mystery about who he was.
Except it was pretty much obvious from the start that it was gonna be Captain Atom, as the story did a bad job of toeing the line between hinting at its big secret and showing its cards too early - and a leak put the nail in the coffin of the secret being kept long enough to preserve the suspense.
So DC pivoted at the last minute, and changed Monarch's secret identity to Hank Hall, the hero known as Hawk (one-half of Hawk & Dove), confounding and disappointing readers and critics alike as the reveal made little sense in the context of the story.
DC later revived Monarch in the story Countdown in which he actually was Captain Atom - but fans and readers didn't like that story any better than Armageddon 2001.
The Thunderbolts put an interesting twist on the concept of characters whose identities are hidden from readers, as most readers didn't realize until the end of the story that they - and the entire Marvel Universe - were being fooled by the new superhero team.
The Thunderbolts, who showed up when the Avengers and Fantastic Four were missing in a pocket reality and presumed dead in the late '90s, were hailed as global heroes - and Marvel's advertising for the title went right along with the idea that they were a group of totally new characters.
That all changed at the end of Thunderbolts #1 - which we'll say is still, to this day, the greatest and most fun trick Marvel ever pulled on its readers - when it was revealed that the members of the team were all secretly the Avengers old foes the Masters of Evil in disguise, being led by Baron Zemo in a scheme of world conquest.
Marvel Studios has a Thunderbolts movie in the works, but the roster is far different from the original comic book team. Still, we've got every reason to expect some kind of twist from the movie.
Spider-Man has a long history with Goblins. Not the feisty little D&D creatures, but a whole dynasty of eerie and macabre supervillains stretching back to his earliest adventures in the '60s with the Green Goblin.
For modern Spider-fans, Norman Osborn and the Green Goblin are inextricable, and at this point, Osborn has menaced Spider-Man in his own civilian guise almost as much as in his ghoulish alter ego.
But when he was introduced, his secret identity was a mystery to both Spider-Man and to readers - with writer Stan Lee's intended reveal that he was secretly Norman Osborn, the father of Spider-Man's best friend Harry Osborn, so controversial to writer and artist Steve Ditko that it led to his departure from Spider-Man entirely.
That tradition - including its controversial ending - continued in the '80s with the introduction of a spin-off villain known as the Hobgoblin, whose secret identity became a long-running subplot in Amazing Spider-Man.
It was initially intended (and seeded in the story) that Hobgoblin would be revealed as supporting character Roderick Kingsley - but the story was changed to a bait-and-switch at the last second with the reveal that it was Peter Parker's pal Ned Leeds in the costume. This was later retconned as Kingsley framing Leeds, though Leeds' connection to the Hobgoblin is part of the current plot of Amazing Spider-Man.
The trick has been repeated a few times since with other Goblin spin-off characters including Menace and Queen Goblin - and now, the upcoming Dark Web story will introduce a new Hobgoblin spin-off villain named Hallow's Eve, whose own identity has yet to be revealed.
Hobgoblin and Green Goblin both make the list of the best Spider-Man villains ever.