It always puzzles me when people assume they can't understand a story unless they read every prior work it makes reference to. I mean, name a single work of fiction that doesn't reference earlier events, even when those events were unchronicled. "The Cage," the very first Star Trek episode ever made, is largely driven by Captain Pike's reaction to a prior event we never saw, the battle on Rigel VII where his yeoman was killed and Spock was injured. But we didn't need to actually see that battle to understand why Pike was world-weary and Spock was limping; it was enough to know that it had happened. Same with any other work of fiction. We don't need to witness the reign and murder of Hamlet's father, or see how Hamlet, Horatio, Rosenkrantz, and Guildenstern went to school together, to understand their motivations and relationships in the play. In Casablanca, we don't need to have seen how Rick Blaine established his relationships with Renault, Ugarte, and Ferrari to understand why he relates to them the way he does, or to have witnessed Victor Laszlo's past acts of heroism to understand why Ilsa loves him and supports his cause. There isn't a story in the history of fiction that doesn't rely to some extent on previously established events in the characters' lives that we never get to see. So why fans think that a story referring back to past events is somehow doing it wrong, or forcing them to gain a complete, detailed understanding of those events before they can read the story in question, is a constant source of bewilderment to me.