Short for “retroactive continuity”, retcon is a term referring to new information added to existing historical material in a work of fiction which is usually of serial character. The actual change – such as the one shown above, with young Anakin (Hayden Christiansen) in the frame where formerly we could see old Anakin (Sebastian Shaw) is called a retcon, while the act or acts of placing retcons into a narrative goes by the name of retconning.

Another example from Star Wars is the insertion of a brief scene between a CGI Jabba the Hutt and Han Solo into Episode IV: A New Hope. It might be seen as counterproductive as it unbalances a beautifully timed and edited sequence and waters down the shock of seeing Jabba in his lair for the first time in Return of the Jedi. The reason for this particular retcon, however, was the testing of Lucas’ new technology: if a credible CGI Jabba (as distinct from the rubber one in Return of the Jedi could be created, Industrial Light and Magic could go ahead with their ambitious plans for a CGI Yoda, CGI landscapes and cityscapes on a colossal scale.

Retconning was first used in comics, such as Marvel Comics or DC Comics. For a longer article on retconning, see Wikipedia.