After Crisis on Infinite Earths, Pre-Crisis continuity (as it became known) became this. And yet, writers sometimes skirted around this, such as when the Pre-Crisis Supergirl somehow was able to travel to Post-Crisis continuity in Many Happy Returns, raising the question of whether it actually ceased to exist, or just got... cosmically buried somehow. Now that the New 52 is in place, one could be left wondering the exact same questions about the 1986-2011 Post-Crisis continuity... until Doomsday Clock revealed that each cosmic crisis spawns a duplicate of the original Earth.
Lampshaded in Grant Morrison's run. Animal Man meets the previous version of himself from another continuity during a peyote trip. The same storyline has him meetGrant Morrison later in the series, at which point Morrison explains that the continuity differences come from different writers writing the same character for different comics. It also features a character - Psycho Pirate - who remembers all the alternate continuities that have ever existed, and goes crazy as a result.
When Animal Man was reinstated to the main DCU, a fair amount of the events of his comic from the Vertigo era were discarded, particularly Buddy's time as a beaked chimera attempting to punish humanity for their crimes against the environment and his falling out with his wife Ellen that resulted in him getting another woman named Annie Cassidy pregnant.
Keith Giffen's infamous "Five Years Later" Time Skip in the fourth volume was motivated by his desire to avoid the many dangling plot threads left over from Paul Levitz' run.
The fifth volume in general and The Dominator War storyline in particular references several events of DC's history: Invasion and 52, the antics of Booster Gold, Let My People Grow!, Mon-El meeting Supergirl in the past before being sent into the Zone by Superman... Said continuity nods make no sense after Legion of 3 Worlds retconned this Legion into being the future of Superboy-Prime's universe.
The 2006 series has been largely ignored in The DCU continuity. With the 2009 series continuing the original series, it seems the 2006 series has slipped completely into this realm.
Mike Grell's 1992 mini-series off-handedly dismissed the death of Tara, which occurred in issues after Grell left the original series.
The new series seems to ignore Mariah's decision to willingly partner herself with a man who physically abused her. Grell has restored her to her original Action GirlAdventurer Archaeologist persona.
The series was almost discontinuity. Grant Morrison's Seven Soldiers led into Final Crisis but Countdown did not. However, Morrison (who also wrote Final Crisis) was forced to cave in and acknowledge Countdown via a time loop scenario: Darkseid wasn't killed at the end of Countdown but thrown backwards in time and possessed the mobster who would become Boss Dark Side, resurrecting his minions in human bodies and consolidating his power base while waiting for his "death" so that he could kill his son and bring the corrupted-by-regular-Darkseid Mary Marvel into his inner circle. Alternatively, Darkseid fell backwards through time after the events of Jim Starlin's Death of the New Gods... but Morrison has stated that the true final war of the New Gods was fought on a higher plane than mere mortals could comprehend, and that both Countdown and DoTNG were merely the mortal characters'/writers'/artists' hopelessly limited, three-dimensional perception of what really happened.
To name a few plot points that were changed post-Countdown to Final Crisis, during Jason Todd, Kyle Rayner and Donna Troy's search for Ray Palmer throughout The Multiverse, they stop by Earth-15, and leave upon learning Palmer's not there. Soon, Superboy-Prime appears and destroys Earth-15. Later, the heroes finally find Palmer on Earth-51, which is described as a "perfect world". Palmer refuses to leave because he's living an ideal life, only for Solomon and the other Monitors to invade the universe. Superboy-Prime then appears and fights Solomon, culminating with him causing the destruction of Earth-51. The heroes then spend the next few issues at Apokolips before being apparently sent to their home Earth. However, it appeared that this is not actually the Earth they live in, and soon the Great Disaster occurs. Afterwards it was revealed that this was Earth-51, reconstructed somehow. As for the retcon, The Multiversity Guidebook simplifies these events so that Superboy-Prime only destroyed Earth-15, which was designated the perfect world, and the Earth-51 where the Great Disaster occurred was never destroyed and recreated beforehand.
Years before the Continuity Snarl of Hawkman, there was a story, in the original Silver Age 1960s Hawkman series, which threatened to reveal Carter Hall's identity as Hawkman. He ended up protecting his identity, but publicly revealing that he's a space alien. Needless to say, this was ignored later.
An odd example is Sovereign Seven, a team of humanoid aliens created by Chris Claremont for DC Comics. They were part of the GenesisCrisis Crossover, and at one point, Power Girl became a member of the team. And then, in the final issue, it turned out they were entirely fictional within the DCU. This appears to have been for the opposite reason than most; Claremont wanted to separate his (creator-owned) characters from The 'Verse once his book was cancelled.
DC Comics has a series of books entitled The Greatest Stories Ever Told, each featuring one character or theme. A Batman volume came out in the late 80s, followed by a volume 2 in the early 90s. V2 was released opposite Batman Returns, and features all Catwoman and Penguin stories. Decades later, DC revived its Greatest Stories series, reprinting the first Batman volume... and produced an entirely new Greatest Batman Stories Volume 2, shoving the previous V2 into no-man's land. (By amusing coincidence, the first volume of Batman stories was the second Greatest Stories volume overall (after Superman), and thus had Greatest Stories Volume Two on the spine. So, at a casual glance, all three different books appear to be "Volume Two" of the same series.)
DC ran an event called Origins & Omens, which had each book featuring an ominous short story hinting at future plots. The Teen Titans story featured several major revelations, such as Static joining the Titans, Blue Beetle kissing Wonder Girl, Sun Girl becoming pregnant with Inertia's child, and Kid Devil being turned into a withered husk. With the exception of the Static bit, literally all of these plot points were ignored.
Superman's career as Superboy gets this treatment a fair amount. Post-Crisis, it is established that he was never Superboy and only started his superhero career as an adult, going by Superman. This caused problems for the Legion of Super-Heroes, who are specifically inspired by Superboy. Thus, the Pocket Universe was born, which would later give birth to Matrix, the first Post-Crisis Supergirl, when its Earth was later destroyed by its Krypton's Phantom Zone criminals. Post-Infinite Crisis, Clark was indeed Superboy again, and this also brought the return of the original Legion. Post-Flashpoint, he was once again never Superboy, with him starting his career in Metropolis as an adult. Then Doomsday Clock revealed why he was never Superboy in the New 52: Pa Kent dissuaded him from it because he'd be the first superhero and thus a freak. When the Justice Society of America are restored to continuity, their presence in WWII made superheroes more accepted, so Pa Kent encourages Clark and he is once again Superboy.
In The Supergirl from Krypton (2004), Jeph Loeb had Kara Zor-El arriving on Earth naked. Supergirl writer Sterling Gates retconned this quietly in Supergirl's Post-Crisis book during his critically acclaimed run, establishing she wore clothes during her space trip, and it was never brought up again. In the same way, most of the stories written by Jeph Loeb and Joe Kelly are disregarded by writers and fans alike.
Similarly, after Kara Zor-El's return, neither of her Post-Crisis replacements make appearances (except for one showing of the kind which fans chose to ignore in the 2009 Reign in Hell mini-series), are mentioned or alluded to by any character, and it was believed DC had quietly retconned them out. Their existence would be effectively erased by the post-2011 universe reboots.
Adventures of Supergirl, a tie-in comic set between the two first seasons of Supergirl (2015), introduces Psi, a Supergirl's enemy originating from Supergirl (1982). The show's third season would introduce Psi, reimagined as a completely different character, making no mention whatsoever to the one who had showed up in the comic.
In Supergirl's Three Super Girl-Friends, Brainiac 5 narrates how his evil ancestor was finally defeated by Superman... though, his account would be ignored by the next Superman writers, (although Let My People Grow! would recycle the "Brainiac accidentally shrank himself into oblivion" bit); Whatever Happened to the Man of Tomorrow?, wherein that incarnation of Brainiac was beaten for good, features a very different scenario.
The Living Legends of Superman: The year 2,491 sequence, wherein humans have suffered under the yoke of a brutal dictatorship for such a long time that they have forgotten what freedom is, ignores the existence of both the Superman Dynasty and Klar Ken -alias Superman XIX- whose stories showed a completely different and more hopeful 25th century since they would have never allowed such a situation.
A storyline in Justice League Europe revealed that Power Girl's frosty and rude behavior was the result of chemicals in a popular soda (diet root beer) she enjoyed drinking, leading to the character becoming more personable once she kicked her habit. This was completely ignored by later writers, who brought back her rude, condescending personality with no real explanation.
Following DC Rebirth, the New 52 Superman and Lois who died and the pre-Flashpoint Superman and Lois who made it to the new universe via Convergence and had a kid were merged. The New 52 Superman stories are mostly still canon in Broad Strokes, but his romantic relationship with Wonder Woman absolutely never happened, meaning a large chunk of his own book prior to his death and literally all of Superman and Wonder Woman are no longer canon.
Adam Strange's late Eighties turn to the Darker and Edgier has become this, as most later writers ignored the ideas in it (other than the introduction of Aleea, Adam and Alanna's daughter). Oddly, however, all five issues of this phase have been reprinted by DC in glossy full color, unlike almost any other Adam Strange stories.
Played with in regards to Batman: Son of the Demon: The story was originally canonical. Then the editors decided they didn't like the idea of Batman and Talia having a child together and it was declared an Elseworlds story, removing it from continuity.note which didn't stop both Kingdom Come and Brotherhood of the Bat featuring grown-up versions of the child, since they were Elseworlds themselves; although Kingdom Come was supposed to be a possible future of the then-canon DCU. Then it was made canon again in 2006 to explain the conception of their young son Damian, but was significantly retconned:note (as writer Grant Morrison admitted to not re-reading Son of the Demon before writing it back into continuity) Batman and Talia's consensual encounter was changed to Talia drugging and raping Bruce, and instead of the child being secretly adopted by an anonymous American couple it was revealed that Talia was raising him all along without Bruce's knowledge.
This has occurred to Betty Kane as Batgirl. While it's true Barbara Gordon was the first Batgirl to have all the main Batgirl traits, the first Batgirl (or "Bat-Girl" as it was spelled then) was Batwoman's pre-Crisis Kid Sidekick Betty Kane. When Crisis hit, DC decided to retcon Betty's existence as Batgirl away. Barbara was chronologically the first Batgirl and Betty never even took up the mantle. Instead, Bette (as she was renamed) became the superhero Flamebird. Bette is still technically a part of the "Bat Family", and her past as Bat-Girl eventually crept back into continuity, but fans look her over and this is rarely brought up.
John Byrne rebooted the entire franchise with his run, and nothing before is even remotely canonical. Fan reception was not positive, to say the least, which led to...
John Byrne's run specifically not being considered canonical by the subsequent creative teams, but everything it retconned out is indeed still canon. Keith Giffen's run even brings back Crazy Jane from the Grant Morrison run, who didn't exist in the Byrne run. Unfortunately...
The New 52 reboot seemed to have retconned the team out of existence. Niles Caulder shows up in The Ravagersseverely de-aged and Danny the Street is, well, a street again instead of a planet with no explanation as to why. Similarly, Beast Boy's origin is completely changed and no longer involves him being adopted by Mento and Elasti-Girl of the Doom Patrol. However...
The Doom Patrol, including Niles Caulder later appear in Geoff Johns' Justice League run and Forever Evil. League featured an older Niles Caulder than the one in Ravagers, and he is indeed in charge of the Doom Patrol. However, fan reaction to the portrayal of the team was... mixed, to say the least, as Caulder was portrayed as an absolute bully to the team, whereas he was previously a manipulator who at least pretended that he cared about them and their feelings. Eventually, this version would be regarded as not canonical as well, with...
Gerard Way's Doom Patrol (2016), the debut title of the Young Animal imprint! At first, it seemed like Way's DP would be a complete Continuity Reboot, in a similar vein to Byrne's. However, it is later revealed that everything except the Byrne and New 52 stuff is canonical, as the characters make specific reference to the Grant Morrison and Keith Giffen runs, and some stories even act as sequels to those runs.
The comic was DC Comics' first official Post-Crisis reboot of the origin of Captain Marvel until years later when it was replaced by The Power of Shazam! by Jerry Ordway. Notably, while this carefully left Marvel's other post-Crisis appearances untouched, it removed Black Adam's significant role in the War of the GodsCrisis Crossover, establishing that Adam didn't have his powers between Billy's origin story and his return in the PoS ongoing.
Crisis Compendium places (or maybe dumps) this story on "Earth-85", along with other early post-Crisis stories that got contradicted by later events, such as Catwoman: The Tin Roof Club (which has Selina wearing her pre-Crisis purple-and-green costume, and features the death of Holly Robinson) and everyone's favourite Continuity Snarl, Hawkman.
Crisis Compendium declared that a large number of Earth-One stories that fell into this took place on "Earth-Thirty-Two", or "Earth-B." This includes, among other things, Superman being revealed to be subconsciously hypnotizing people to make them think he didn't look like Clark Kent, Flash getting his powers from a Mxyzptlk knockoff named Mopee, Batman having a brain-damaged serial killer brother, and a variety of stories that didn't have any obvious "place" or contradicted existing material, such as The Golden Age and the tie-in comic to the Super Powers toyline.
In a bizarre semi-Word of God example, Mike W. Barr responded to a letter in an issue of Batman and the Outsiders wondering why Metamorpho didn't know Batman's secret identity when a previous story had Metamorpho delivering Batman's costume to Bruce Wayne. Barr declared that story to be out of continuity and further stated that any story previously published that contradicted one of his stories was by definition out of continuity.
Donna Troy gets hit with this so often she's ended up with her own Continuity Snarl page, as writers try to get rid of and replace her origin, starting with the first - and fan preferred - one presented in Who Is Donna Troy?, and often end up contradicting current canon in doing so.
Wonder Woman (Rebirth): With "Year One" acting as Diana's true origin, the Amazons' kidnapping sailors and raping them to produce children during Brian Azzarello's run is no longer true. "The Lies" suggests that basically everything Diana thinks she remembers (i.e. her entire New 52 backstory) is false.
Deathstroke: The DC Rebirth series ignores everything Deathstroke-related that had been established in the New 52, which included Rose Wilson suddenly being fully white and the daughter of Slade Wilson and Adeline Kane, her history with Harvest and the weird contradictory backstories of the Wilson family in the two New 52 Deathstroke series, including which of Slade's kids were alive. Instead, Rebirth basically restores the original relationships and updates them a bit, with the only reference to the New 52 stuff being a joke about Slade having had black hair at some point (this was done to make him appear more like his Arrowverse counterpart when it was a thing).
Many New 52 Bat-Family origins, and some of its villains', are either this or Broad Strokes:
Dick Grayson's new origin saw him start at an older age and develop a personal rivalry with Lady Shiva. In Rebirth, Dick is shown to have started at the younger age he usually starts at once again, and his supposed rivalry with Shiva isn't mentioned by either of them.
Tim Drake's new origin saw "Tim" put into witness protection after he, being a child prodigy eager to get Batman's attention as Batman was looking for a new partner, provoked the Penguin and had his house shot up as a result. His parents were put into witness protection, and Tim assumed the last name "Drake", and became Batman's new partner, Red Robin. In Rebirth and Infinite Frontier, Tim is once again the normal Robin who actively sought out the role of Batman's partner after Jason Todd's death, and no mention is made of his apparent fake name — he'd also later mention his dead father, something that only happened pre-Flashpoint.
Catwoman's new origin has her having a missing brother and moonlighting as an office worker before becoming Catwoman in a pseudo-recreation of her Batman Returns origin. While it's possible some of this is still the case, Selina has never mentioned a brother again, and future stories reiterate her being a prostitute alongside Holly Robinson like in "Year One", and outright lift entire scenes from said story.
Mr. Freeze had his origin altered so that he never had a wife called Nora who he tragically had to freeze to keep from dying — she's now a random woman suffering from a terminal illness and he projects his sick obsession with cold onto her. This was only ever mentioned in one issue, and Freeze was barely used in the New 52. Once DC Rebirth started, Scott Snyder, one of the writers who wrote the New 52 origin to begin with, had Batman refer to Nora as Freeze's wife with no mention of the prior origin, and later still Peter J. Tomasi would have Nora thawed out and she very clearly is Victor's wife, and Bruce himself mentions Freeze's original origin, so there is no mistaking that the New 52 origin was removed.
This kind of happened to the Joker thanks to the dubiously canon Batman: Three Jokers. The New 52 origin had the Joker be the leader of the "Red Hood Gang" prior to leaping into a vat of chemicals to escape Batman. Three Jokers reiterates that the modern Joker was a failed comedian who fell into the vat after a string of unfortunate events, just as in The Killing Joke.
The Flash removed the entirety of the New 52 Eobard Thawne's backstory. In the New 52, Eobard Thawne was the supervillain Zoom (he never went by Reverse-Flash this time), from a Bad Future where he fought against people who worshipped the Flash. He travelled back in time and murdered Barry's mother and gathered a bunch of acolytes, wanting to defeat Barry, and was defeated and imprisoned. In Rebirth, he's struck by energy from Doctor Manhattan which somehow brings back the pre-New 52 Eobard Thawne's memories, personality and origin, returning him to a deranged Flash fanboy from the future who desperately wanted to be the Flash and lashed out when Barry stopped his abuse of his powers in the future. No mention has ever been made again of anything of his New 52 origin, and he once again goes by Reverse-Flash.
The aforementioned Batman: Three Jokers was itself subjected to this in this run. While Geoff Johns pulled a Shrug of God about Three Jokers being canon, Zdarsky's "Joker: Year One" arc flatout subjects it to this trope, walking back the idea of there being three Jokers, first hinted at the end of "Darkseid War", by revealing the "three Jokers" revelation wasn't literal, but merely referring to the Joker having trained to create split personalities at will; he's still one man, but with three different personalities.
On the flip side, the events of Batman's trip through the multiverse that included the resurrection of various versions of the Joker is ignored by one of those universes as one of the Jokers revived on-panel is the Batman: Arkham Series Joker — whereas Suicide Squad: Kill the Justice League, also set in the Arkham universe, treats its universe's Joker as still dead.
", or "Earth-B." This includes, among other things, Superman being revealed to be subconsciously hypnotizing people to make them think he didn't look like Clark Kent, Flash getting his powers from a Mxyzptlk knockoff named Mopee, Batman having a brain-damaged serial killer brother, and a variety of stories that didn't have any obvious "place" or contradicted existing material, such as The Golden Age and the tie-in comic to the Super Powers toyline.