Marvel's Spider-Man often falls victim to retcons, but the worst one of all ruined the Green Goblin, Aunt May and Peter Parker all in one ignominious issue. Retroactive continuity, or a retcon, is a term used by fans to describe the constantly-changing history of comic book characters (usually when a new writer is hired to take over an existing storyline). Spider-Man is subject to more retcons than most superheroes, but in Spectacular Spider-Man #263, readers were shocked as the issue erased all the events of the well-received Amazing Spider-Man #400.
In Amazing Spider-Man #400, a landmark issue with a white cover, Aunt May is released from the hospital after suffering a stroke. Both May and Peter make their way to the top of the Empire State Building at which point May confesses she's always known Peter was Spider-Man (Peter tries to deny it at first, but quickly realizes it's impossible to keep a secret from one's surrogate mother). Aunt May admits she was worried at first, but when she saw all the good that Peter achieved as Spider-Man, she couldn't be more proud of her nephew. The two embrace, but Aunt May grows tired and the two head home. Later that night, Aunt May dies peacefully in her bed.
To see a long-running character like Aunt May pass away after 30 years of comic history shocked the Spider-Man faithful, but ultimate the issue was highly-regarded; the moment was treated with dignity and fans were excited for a new chapter in Peter's life. That excitement came to a screeching halt with the release of Spectacular Spider-Man #263 - in which the Green Goblin (newly resurrected after the controversial Clone Saga) revealed the truth: Aunt May was not dead, and the woman who died in her stead was a genetically-altered actress hired by the Goblin. Even in a world populated with aliens, clones and thunder gods, this reveal strained plausibility.
According to the Goblin, the actress "...studied May's mannerisms and voice inflections over months until the two women were indistinguishable." Furthermore, the Goblin told the actress about Spider-Man's dual identity, knowing she would mention it to him. This means that May's confession - regarded as one of the most heartwarming moments in Spider-Man's life - never happened. When Peter found the real Aunt May once again, she was once again completely unaware as to Spider-Man's secret identity and status quo was reestablished.
Spider-Man may constantly fight against villains like the Green Goblin, but another, more sinister battle occurs in the shadows - between the writers who wish Spider-Man to grow up and take the next step in life, and those who desire to maintain his status quo in the name of the ever-elusive relatability. The latter side won out in the case of the contentious Spider-Man: One More Day and with Spectacular Spider-Man #263 as well. When the Green Goblin laughs after delivering the reveal, he wasn't aware that readers Spider-Man's latest retcon were laughing as well...though perhaps not for the same reason.