Retcon

Retroactive continuity (or retcon for short) is when the previously established events in a continuity are later altered by the writers.

Examples

• In episode 57 of the Chaotic Century anime, Raven and Rease are killed when they are enveloped by a charged particle beam fired by Hiltz. Later, in episode 63, Raven and Rease are shown to have survived.
• In the first half of Zoids: Chaotic Century, it is directly implied that Prozen's Death Saurer was the same one that wiped out the Ancient Zoidians: Prozen is said to have "resurrected" the Death Saurer rather than created another, and the Death Saurer itself awakens prematurely in response to Fiona's presence. Much later in episode 65, it is revealed that Prozen's Death Saurer was merely a clone of the original.
• Zoids: Fuzors was clearly written as a standalone entry in the franchise, but when Tomy released its Zoids: Fuzors toyline, it was placed in the same timeline as the Battle Story, taking place during the Three Tigers era. This creates numerous plot holes, as certain Zoids which are portrayed as new in Fuzors (such as the Liger Zero Phoenix, Gairyuki, Seismosaurus, etc) predate the Three Tigers era by over 120 years!