A popular arc featured a warped and bizarre Metropolis in which the villainous Superman every night busted out and had to be brought back to jail by the resident superhero, Bizarro. The reason behind this sudden change and the entity responsible? The mystery was tightly kept during the original release, but the fact that the paperback collection was titled Emperor Joker ruined the big surprise.
Given the fact that Krypton No More was published in 1976 and the fact that Krypton is still a part of the lore, the fact that titular event is a lie devised by Supergirl and the citizens of Kandor as a (really fucked-up) way to get Superman to stop stressing out when he starts veering close to eco-terrorism.
The trade paperback for one Transformers story was called Transformers: Legacy of Unicron. This was a big deal when the comic was first published: the title was blanked in the table of contents.
When Mary Jane first appeared, she was initially The Faceless, and the fact that she was a complete fox instead of just plain was a huge surprise to Peter Parker as well as his friends ("Face it, tiger; You just hit the jackpot"). Now that the cat's been out of the bag for years, it's virtually impossible to view this as a surprise thanks to her immense popularity as well as her countless depictions in the media.note Although Spider-Man #42 was the first time Peter—and the readers—saw Mary Jane's face, other characters had previously remarked that she was gorgeous. Still, she was first mentioned in Amazing Spider-Man #15 and the first indication that she was pretty came ten issues later, with another 17 issues before Peter and the readers met her.
The Green Goblin's identity was a secret for over two years (in real time). He debuted in Amazing Spider-Man #14 and wouldn't be revealed as Norman Osborn until #39. Now everyone with more than a passing knowledge of Spider-Man knows Norman is the Green Goblin.
The trade paperback for Marvel 1602 has a foreword by a critic. While it doesn't quite spoil the ending it does a large part of the middle; namely, the death of Queen Elizabeth, and that the heroes end up in America.
There's something about Neil Gaiman and spoileriffic forewords.
Frank McConnell's foreword to the The Sandman (1989) trade paperback "The Kindly Ones" actually features the line, "Dream dies at the end." Not only that, but McConnell is utterly unapologetic about spoiling it for people who haven't read the comic yet: "Sorry to bust your bubble, but this is a tragedy, or at least, as classically tragedy has been written in a long time, so you should know at the outset how it's going to end." Thanks, Frank, but if Neil Gaiman felt that way, he probably would have started with that scene and flashed back, or had a Greek chorus tell us how the arc would end, or do anything but tell the story in a chronological fashion.
There is a clue in an earlier comic: Destiny looks in his book and sees an image of "Dream, clothed all in white and with white hair.". There's also the scene that closes the arc immediately before the Kindly Ones, at the Inn At World's End. After all the travelers have told their stories, all the characters are distracted by a literally massive funeral procession dominating the horizon. In that procession are all of Dream's family and many recognizable faces from previous stories, including characters that only exist because of their ties to Dream, such as Melvyn Pumpkinhead, Nuala, et al. If you look - not even carefully, if you just look, it becomes swiftly impossible not to notice that ALL of these characters are closely tied to Dream... and Dream is the only character not present in the procession. The sequence ends with an image of Death, crying. The sequence did not so much 'heavily foreshadow' Dream's death as much as it outright told you it was going to happen.
This isn't limited to the Kindly Ones. Every trade except the first volume contains an introduction and while some warn, all of them outright spoil the stories contained inside.
The title of the first post-Civil War (2006)Captain America TPB? Captain America: The Death of Captain America. While yes, there was a huge media blitz about it when it happened, it kind of sucks for new readers, or people in other countries who didn't get that hype.
Then it happened again, only in reverse. With the delays on Captain America: Reborn, he appeared in at least four books before the big event had actually happened.
And then: Cap was revealed to have been a Hydra agent all along, via Red Skull manipulating a sapient, but juvenille Cosmic Cube into making it so. Though it isn't clear whether or not Kobik changed Cap's memories (with Red Skull giving the other Hydra agents the heads up) or changed the actual timeline.
The Robin (1993) trade paperback that features the return of Spoiler has this plastered on everywhere. The Spoiler alert tag itself is a spoiler. Spoiler is on the cover. Then inside, the reader discovers very quickly that without doubt it's Stephanie Brown. So it's more about Robin's reaction to and refusal to believe it.
Legion of Super-Heroes storyline, The Great Darkness Saga featured Darkseid as the main antagonist. His appearance intended as a surprise is blown to anyone who picks up the trade (as he appears on the cover).
The back cover of the paperback collection Annihilation Conquest: Book Two refers to "the previously unknown mastermind of the Phalanx invasion — a revelation that will have longtime Marvel fans' jaws on the floor!" The illustration immediately below this text plainly shows the evil robot Ultron.
Back in the 1960s in The Avengers, a new character called "Yellowjacket" appeared, claimed that he had killed Henry Pym, kidnapped the Wasp, and to everybody's surprise, when they returned the Wasp organized a wedding with him. It was revealed that end of the story that Yellowjacket is Henry Pym, with a Split Personality. Still, after being cured from the split personality problem, he kept being "Yellowjacket" as his superhero identity (or at least, one of the several he had over the years). For this reason, hardly any modern reader of the Avengers will read the TPB and not realize what was really going on long before the reveal.
When NYX was originally released, X-23 was unknown in the comics and had thus far only appeared in two episodes of X-Men: Evolution, making it a legitimate surprise when she is revealed as the identity of the prostitute who appears in issue #3. Now, that NYX was her comics debut is about the only thing anyone actually remembers about the series. The trade paperback collection even plasters her quite prominently right on the cover, even though Kiden Nixon is the main character and the number of times Laura actually has lines can be counted on one hand (though she does ultimately drive the plot in the second half of the story).
When The Judas Contract of the Teen Titans was first published, nobody suspected that Terra, the Naïve Newcomer, would actually be an evil spy. Nowadays, her betrayal has been a recurring past plot for the Titans, and any betrayal (real or supposed) is compared with Terra's. Even more, there was a clone of Terra some years later, always living under the shadow of the actions of the original one. It is unlikely that a modern reader would read the story without knowing in advance what was going to happen.
In one story, the X-Men find themselves in the Savage Land, in the company of a white-haired but not-too-old-looking man. Eventually he puts on a certain familiar helmet. At the time it was a major shocker, because the audience had never seen Magneto unmasked or not acting like anything other than a hammy villain. It was a very effective disguise. Of course, now, we know Erik's face as well as his costume (even Depending on the Artist doesn't change his most distinctive aspects to the point of him being hard to recognize, just like there's no not knowing Wolverine no matter who's drawing.) to the point that a much later story where he went incognito had him dramatically unmasked with his real face, no costume needed. It isn't just unsurprising; you'll spend the whole story confused that nobody's reacting like they should until you get to The Reveal and realize this is the first time they saw him.
Similarly, Jason Wyngarde from The Dark Phoenix Saga. This mysterious behind-the-scenes player has a long-term scheme unfolding over many issues (this is before the Decompressed Comic; several issues meant several stories.) Then we discover he's part of a group called the Hellfire Club, and we meet Emma Frost and the Club wants the then-newly-encountered Kitty Pryde and it's only when the Hellfire Club arc is in full swing that we get The Reveal that the mastermind of their plan was... well, Mastermind. Their loooooooong-unseen old enemy used his Master of Illusion powers to take on a posh appearance and a new alter ego. Of course, as with the above example, we've known who he is for so long that it's impossible to not know who he is from the beginning of the story. In fact, any time they've run into him since then, someone will always say "remember when you did that thing to Phoenix that resulted in her going apocalyptically nutso?! You're going down for that!"
And for that matter, spoiler alert: Jean Grey is going to get supercharged and become Phoenix. Then she's gonna go apocalyptically nutso. And die. And get better. Each of those things was a surprise at the time, each a major game-changer and a milestone moment for the franchise.
The first big twist in the 2019 X-Men: The Krakoan Age mega-arc is that Moira MacTaggert, the human geneticist who's been one of their closest allies since 1975's Uncanny X-Men, isn't human. She's a mutant with Resurrective Immortality who's a living Reset Button, returning the timeline to the point of her birth each time she dies. Krakoa is her tenth attempt to create a timeline where the mutants win. Almost everything that follows is built around that reveal, with major Call Backs to the way that several of her previous lives failed.
Transformers: More than Meets the Eye got hit with this hard when Megatron joined the Lost Light crew at the start of season 2. Not only did IDW itself spoil him joining the crew through solicitations, but the cover for volume 6 prominently displays Megatron with an Autobot symbol. Just to make it worse IDW spoiled this before the story it occurs in was over. This Very Wiki has this problem. The pages for MTMTE were blanking out Megatron's joining with spoiler tags, but his role was so big and he was so thoroughly spoiled that it was decided there was no point in blanking out everything.
The Avengers (Jonathan Hickman) featured The Illuminati trying to stop 'Incursions', the collision of alternate universe Earths, the result of which is the destruction of both universes that the Earths belonged to. We are told that the only way to avert this is to destroy one of the parallel Earths, which spares both universes. The Illuminati set out to stop these Incursions without having to destroy another Earth. However, the explicit premise of Secret Wars (2015), also by Hickman, is that the Incursions were not stopped in time, and that the fragments of the destroyed Multiverse were forged into Battleworld by Doctor Doom. Not only that, but a Secret Wars #0 was given away for free on Free Comic Book Day, and it gave the premise of Secret Wars (2015) away in order to make it friendlier to newer readers, meaning even the most casual of readers knew the Illuminati would fail.
Related to that, due to some rather ridiculous Schedule Slip, Secret Wars was delayed long enough that parts of the ending were already spoiled by the All-New, All-Different Marvel relaunch. The All-New, All-Different Avengers preview given out on Free Comic Book Day already spoiled that certain characters would survive and that Miles Morales would be joining the Marvel Universe, but the first issue of the new Iron Man took it even further by spoiling that Doctor Doom survived the events of Secret Wars, and has healed his face to boot!
The Metal Gear Solid 2: Sons of Liberty graphic novel adaptation casually spoils the reveal that Raiden used to be the legendary child soldier Jack the Ripper in Raiden's introductory scene. It also spoils The Sorrow being Ocelot's father, though it's not particularly clear why this is significant to someone who doesn't know the sequel.
A Golden AgeCaptain Marvel serial featured the monster society of evil, and their mysterious leader, Mister Mind. The story ran for two years, being the first superhero story to ever be divided in more than one book. When it was revealed Mister Mind was actually a silly-looking worm, it was a comical twist. Now, it's the first thing known about the character.
When "Ultimate Nightmare" was first released, it was not marketed as a story about Galactus in any way. As a result, when the Vision says what was it all about, it was a genuine surprise for the audience. Now, with the miniseries and the two following ones being sold as the "Ultimate Galactus Trilogy", it is no surprise that it involves Galactus.
The second arc of Rat Queens has a major reveal when Hannah takes down her hair, showing the stubs of her demon horns. By the fourth arc cover artwork routinely shows her horns.
Part of the run deals with the aftermath of Batman (Tom King) and how it affects Batman — including Bane's murder of Alfred.
For the rest of the run, there's how The Joker War affected Bruce: the Joker stealing the majority of Bruce's money and gear, and Lucius Fox's family disowning Bruce and being in control of Wayne Enterprises (the latter being part of the premise of The Next Batman: Second Son and I Am Batman).
A Death in the Family: At the time, many people dismissed the voting as a publicity gimmick, and that Robin would naturally live. The ads for issue 4 stated otherwise: "Robin is dead, murdered by the Joker."
◊ Ultimate Fallout #4 keeps Ultimate Spider-Man's unmasked face obscured, leaving it ambiguous if it's Peter Parker Back from the Dead, or a successor. The version for the second printing
