Spoilers for Batman/Superman #22!
Despite being some of the most successful characters of all time, Batman and Superman just made fun of DC Comics and its readers. One of the most recognizable traits of modern-day superhero comics is their decision to reboot the universe. The New 52 years were a perfect example of starting fresh for DC. However, after fans realized New 52 had run its course, and the comics became an excuse to reboot classic stories, they introduced DC Rebirth, which once again rebooted the universe. DC even stated that Rebirth was not a reboot, even though most fans still recognize it as a blatant refresh button.
Batman/Superman #22, by Gene Luen Yang and Paul Pelletier, just put Bruce and Clark against Mr. Mxyzptlk, the wacky imp from the fifth dimension, and Calendar Man, the holiday-obsessed serial killer. Throughout the comic, Mxyzptlk breaks the fourth wall with Calendar Man, which allows Julian Day to look at different panels within the comic book. He discovers Bruce Wayne's identity by reading a scene with Bruce with his cowl off. Calendar Man also uses a pen to alter things within the pages. Batman eventually disarms Calendar Man, but the pen falls through a panel and slices his arm off in the next. At the end of the comic, Mxyzptlk erases Batman's identity from Julian's memory and gives him his arm back, meaning nothing happened.
Mxyzptlk lashes out at the reader at the end of the story, complaining how Batman and Superman always win. Although he's cryptic, what the imp says has some truth to it. Even when the World's Finest superheroes deal with the craziest, multiverse-shattering situations, they either always win in the end, or everything goes back to normal. When Superman "died" in The Death of Superman, it didn't even take a year for him to make his triumphant return. Likewise, when Batman's back broke around the same time, it didn't take long for Bruce to defeat Bane and Azrael and return as Batman.
The Death of Superman, by Dan Jurgens, Jerry Ordway, Mike Carlin, Roger Stern, and several others, is one of the most iconic stories in comic book history. The story was so shocking at the time that it even appeared in the news. When Doomsday and Superman defeated each other, nearly every superhero in the DC Universe attended his funeral. Superboy, Steel, Eradicator, and Cyborg Superman tried to fill the enormous hole left by the Man of Steel. When writers learned how impossible that mission was, they retconned his "death" to a coma and introduce the Kryptonian regeneration matrix, allowing Clark Kent to re-enter the narrative as the original Superman.
Batman's no better, as evidenced by the famous Knightfall storyline. After Bane broke Batman's back, many fans were left to think DC was rebooting Batman as Azrael, AKA Jean-Paul Valley. When Bruce returned to defeat Azrael, he didn't even take up the mantle of Batman right away, allowing Dick Grayson to be the Batman of the 90s for some time. Of course, readers will want the original Bruce Wayne back no matter how good the Dick Grayson Batman stories are. Bruce Wayne eventually returned in Batman #515.
Now, fans are accustomed to constant reboots in DC Comics. Some reboots still remain critically successful though. Crisis on Infinite Earths, the first contemporary superhero comics reboot, reorganized DC Comics into what it is today, allowing the narratives to focus on fresh, character-driven arcs. Despite this, it can still be convoluted to follow rebooted series. Superman and Batman still get Elseworlds stories, though. Limited series like All-Star Superman and The Dark Knight Returns grant writers complete creative liberty to avoid the reboot dilemma.