Definition

Retcon or retroactive continuity is a term that is used when writers reveal something new to a previous story already told which usually changes the original back story to something new. The term "Retroactive Continuity" was made known by All-Star Squadron writer Roy Thomas in the 1980s. Damian Cugley shortened the word to "Retcon" when Alan Moore re-wrote the origins of Swamp Thing in 1988.

List of Retcons

• In Crisis on Infinite Earths after all the alternate Earths were destroyed, many heroes including Superman and Wonder Woman had their entire origins retconned and thus their series rebooted.
  

• In Infinite Crisis: Secret Files, there were several retcons that had an on-panel source. When Superboy Prime punched the barrier of reality he caused changes throughout the DC Universe including the resurrection of Jason Todd and the reboot of the Doom Patrol.

• The original killer of Thomas and Marth Wayne, Joe Chill was captured, however DC retconned it so the killer was never actually captured.
  

• Barbara Gordon was retconned to be Commissioner James Gordon's niece in Batman: Year One. Originally she was Jim's blood-related daughter.

• When Frank Miller took over the run for Daredevil, he retconned Daredevil's history so that Stick, an Asian man, helped him develop and master his new abilities.

• During the Clone Saga, Mary Jane had a baby and Aunt May died at the end of the story arc. When J. Michael Straczynski took over Spider-Man in 2001, he retconned it so those two events "never happened."
  

• Gwen Stacy's past was retconned when J. Michael Straczynski wrote the Sins Past story arc. This revealed that Gwen Stacy had an affair with Norman Osborn when she was in Europe mourning the death of her father.

• The Phoenix Saga was originally created by Chris Claremont for the Phoenix to actually be Jean Grey at the peak of her potential. Years after Jean's death, Marvel wanted to bring Jean back. However, bringing her back at first would bring many complications. If Jean were to be brought back, she would still be guilty for killing millions of life forms. Marvel announced that they would not bring back Jean unless someone creates a suitable resurrection story. Kurt Busiek (then a college student) and a few friends started pitching ideas. Eventually he would retcon Phoenix into a cosmic entity, and while Jean was piloting the shuttle, the Phoenix approached her and made an exact duplicate to use. While also merging with a portion of her soul, therefore freeing Jean from the guilt of murder.

• After the events of Captain Atom: Armegeddon, parts of the WSU were retconned in what was termed a "soft reboot", since not everything was erased. The past stories of some teams and characters, most notably Gen 13, Deathblow and WetWorks were completely restarted, erasing all their previous stories (and connections with other teams and characters) from the history of the Wildstorm Universe. Others, like The Authority and Wildcats, were unaffected, and in a few cases, some characters have vague memories of previous connections with characters that they knew before Armageddon but were involved in the retcon. One character, John Lynch, even seems to know that he (and others) are not the original versions of themselves.