Retroactive Continuity, or Retcon, for short is a term that is all together too common in the comic book world. It basically means that there’s an alteration to an established fact within continuity, and comic book writers use this strategy to add, remove, and of course, alter stories.
With all the stories being written and new creative teams taking the reins for various properties, there always a chance things will get retconned. As a reader, it’s something that I don’t personally enjoy but I understand where publishers and writers are coming from. It sort of reminiscent of the music industry where nothing is original anymore. But with so many talented creatives entering the comic book industry, new stories are being thought up with fresh perspectives such as Scott Snyder’s addition to the Batman canon with his Court of Owls story arc or Francis Manapul’s work on The Flash.
But retcon examples litter the stories we read. A prime example when a writer added something that wasn’t already established within continuity is what Brian Wood began on IDW’s Star Wars before Kieron Gillan picked up the mantle when it moved over to Marvel. Wood started to write stories that involved all our favorite Star Wars characters from the point after the Battle of Yavin, right after Episode 1: A New Hope.