Addition Retcons sometimes do not contradict previously established facts but instead fill in missing background details, usually to support current plot points. Thomas referred to "retroactive continuity" in this sense, as a purely additive process that did not undo any previous work; such additions were common in
All-Star Squadron.
Kurt Busiek took a similar approach with
Untold Tales of Spider-Man, a series which told stories that specifically fit between issues of the original
The Amazing Spider-Man series, sometimes explaining discontinuities between those earlier stories.
John Byrne used a similar structure with
X-Men: The Hidden Years. Possibly the earliest
Marvel Comics example of new stories placed between long-established stories was the 1977–1978 magazine
The Rampaging Hulk. In
The Godfather Part II, the character
Frank Pentangeli is introduced as an old friend of the family though he is not referenced in the first film; similarly
Don Altobello is one of the "old time" Dons, though he is not mentioned until
The Godfather Part III. Neither addition affects the plot line of the previous films. The addition, in later seasons, of an attic to the family's home in
Full House stands as a similar additive example. A similar concept is that of
secret history, in which the events of a story occur within the bounds of already-established events (especially real-world ones), revealing different interpretations of the events. Some of
Tim Powers' novels use secret history, such as
Last Call, which suggests that
Bugsy Siegel's actions were due to his being a modern-day
Fisher King.
Alan Moore's additional information about the
Swamp Thing's origins – revealing that Swamp Thing was not actually scientist Alec Holland converted into a plant, but actually a plant that had absorbed Holland's body and consciousness so that it merely thought it was Holland – did not contradict or change any of the events depicted in the character's previous appearances, but instead changed the reader's interpretation of them. Such additions and reinterpretations are very common in
Doctor Who. only to bring him back, in large part because of readers' responses, with "
The Empty House" in 1903. The character
Zorro was retconned early in his existence. In the original 1919 novel,
The Curse of Capistrano, Zorro ends his adventures by revealing his identity, a plot point that was carried over to the 1920 film adaptation
The Mark of Zorro. In order to have further stories starring Zorro, author
Johnston McCulley kept all the elements of his original story, but retroactively ignored its ending. One notable example is
Isaac Asimov’s 1950
fixup novel
I, Robot, a collection of
science fiction short stories originally published in
Super Science Stories and
Astounding Science Fiction from 1940 to 1950. Compiled into a single publication by
Gnome Press in 1950, the collection features a
framing sequence in which the stories are told to a reporter by Dr.
Susan Calvin, chief
robopsychologist at
U.S. Robots and Mechanical Men, Inc. Changes necessary to fit the new version included the name of the company (originally the Finmark Robot Corporation), new, earlier references to the
Three Laws of Robotics, and new interpolated scenes featuring Dr. Calvin herself. The TV series
Dallas annulled its entire ninth season as just the dream of one of its characters,
Pam Ewing. Writers did this to offer a supposedly plausible reason for the major character of
Bobby Ewing, who had died onscreen at the end of season eight, to be still alive when actor
Patrick Duffy wanted to return to the series. This season is sometimes referred to as the "Dream Season" and was referred to humorously in later TV series such as
Family Guy and
Community as a "gas-leak year". Other series such as
St. Elsewhere,
Newhart, and
Roseanne employed the same technique.
Subtraction Unpopular stories are sometimes later ignored by publishers, and effectively erased from a series' continuity. Later stories may contradict the previous ones or explicitly establish that they never happened. In television, when a character is subtracted with a retcon, this is often known as "
Chuck Cunningham syndrome," after a character from the series
Happy Days that was retconned out of existence shortly through the series run, or "going to Mandyville," after
Mandy Hampton, a character that suffered a similar fate in
The West Wing. Notable examples of subtractive retconning include
Terminator: Dark Fate (2019)
, which is a sequel to the first two
Terminator films and ignores the events of every other film in
the franchise, and
Halloween (2018), which is a sequel to only the
original film and disregards all the other sequels. Stories that involve
time travel can be used to undo the events of poorly received installments. After
X-Men: The Last Stand (2006) faced criticism for abruptly killing off characters such as
Cyclops and
Jean Grey, its sequel,
X-Men: Days of Future Past (2014), features the character
Wolverine traveling back in time to 1973 to prevent an assassination that, if carried out, would lead to mutant extinction. The result of this is a new timeline where Jean and Cyclops never died. ==Related concepts==