There are various motivations for applying retroactive continuity. The changes may occur to accommodate sequels or derivative works, allowing newer authors or creators to revise the diegetic (in-story) history to include a course of events that would not have been possible in the story’s original continuity. Retcons allow for authors to reintroduce popular characters and resolve errors in chronology.
Retcons are common in pulp fiction, especially in comic books published by long-established publishers such as DC and Marvel. The long history of popular titles and the number of writers who contribute stories can often create situations that demand clarification or revision. Retcons also appear in manga, soap operas, serial dramas, movie sequels, professional wrestlingangles, video games, radio series, and other forms of serial fiction.
Science fiction writers are occasionally confronted with new scientific developments that disprove assumptions made in a previous story or book.