All There In The Manual / Star Wars

• The Rule of Two of the Sith is mentioned by Yoda in The Phantom Menace but it is never given any elaboration beyond explaining why we shouldn't expect more than two Sith. Tie-in media and supplementary materials would give a much more detailed account about the Sith, namely that Darth Bane, the last surviving Sith of his time, established the Rule of Two to ensure the Sith's survival from their own backstabbing. Additionally, it's explained that their revenge against the Jedi is a case of Never My Fault since the Sith brought about their own destruction through constant backstabbing for leadership whereas in the films themselves, it's implied that the Sith were directly destroyed by the Jedi and Darth Sidious is only returning the favor during his takeover of the Galactic Republic.
• All the ships, technology, alien species, and individual characters that are briefly seen throughout the movies are given names and backstories somewhere in reference materials, Star Wars Legends and the Star Wars Expanded Universe.
• Aurra Sing appears briefly during the Pod Race sequence in The Phantom Menace. The movie gives no explanation as to who she is, but the comics, novels, games, and The Clone Wars elaborate further on her story.
• Attack of the Clones introduces the concept that the Clones were created after Bounty Hunter Jango Fett, its never explained in the film why the Kaminoans (Or Palpatine) decided to use him as a blueprint for the Clone Army. Its explained in the video game Star Wars: Bounty Hunter (And with more detail in the comic book Jango Fett: Open Seasons)
• The Special Edition of A New Hope has a cameo of Dash Rendar's Outrider, from Shadows of the Empire.
• Lucasfilm seems to enjoy using this trope if for no other reason than to make fans buy all of the various merchandising tie-ins in order to get the whole story. For their The Force Unleashed multimedia project, which was presented primarily as a video game, players never learn the name of Darth Vader's secret apprentice, who is referred to only as "Starkiller"; his real name (Galen Marek) is revealed only in the official novelization, which is considered to be the "canon" version of events. See Shadows of the Empire for similar shenanigans.
• The opening crawl of Revenge of the Sith mentions "There are heroes on both sides. Evil is everywhere", a statement that makes no sense in the context of the prequel films. It would be up to Star Wars: The Clone Wars to elaborate on this in its later seasons. "Heroes on both sides" refers to how both the Republic and Separatists consider themselves to be right and just (the Republic is as corrupt as the Separatists say), with Dooku in particular being a beloved figure to the latter group. "Evil is everywhere" meanwhile refers to Darth Sidious orchestrating the war from both sides (with help from corporations who are in the Republic but are secretly supporting the Separatists), as well as Fallen Jedi like Pong Krell, and Anakin not being the Jedi he should be either.
• Revenge of the Sith begins with Coruscant under attack and recently "kidnapped" Chancellor Palpatine a prisoner on General Grievous's ship. While it's not strictly necessary in order to understand that setup, the first series of Clone Wars cartoons (the Genndy Tartakovsky one, not the CGI one) actually showed his kidnapping. The last episode of that series ends the moment the movie begins. The same cartoon has the introduction for General Grievous; going only by the movies he appears out of nowhere and his presence is never explained.
• On a similar level, Star Wars: The Clone Wars (Movie) assumes you've seen Genndy's 2D series, as it doesn't explain that Anakin is now a Jedi Knight and is the same rank as Obi-Wan ("brothers") rather than his student, hence why Anakin is allowed to have Ahsoka as his padawan. It also gives no introduction to Ventress and how she came under the tutelage of Dooku; she just shows up and everyone already knows her.
• On the flipside, if the viewers read up on the Visual Dictionary by the time The Phantom Menace is released, it would also essentially spoil the fact that Senator Palpatine was the same guy as The Emperor in Return of the Jedi. Something similar happens with the Inside the Worlds of the Original Trilogy guide, where the portion where it shows the Emperor electrocuting Luke has the statement about "Darth Sidious' Crooked Fingers," essentially spoiling the secret of who Darth Sidious was before Revenge of the Sith unveils the revelation that Palpatine and Sidious are the same person.
• The original '70's novelization of A New Hope revealed that the Emperor's name was Palpatine in a brief foreword before the story proper even began. The expanded universe had been using the name quite casually since at least The Thrawn Trilogy.
• Despite how their first appearance in the franchise played a central role in the film, the name of the Ewoks in Return of the Jedi is never mentioned or brought up until the credits start rolling. The main reasons the general public may know their name was through pre-release material and later movies and books.
• In The Force Awakens, C-3PO's red arm is explained in the comic Star Wars Special: C-3PO.
  • Basically nothing is explained in the movie itself. What the First Order is beyond just "the remnants of the Empire", why the Resistance is separate from the Republic, why the destruction of a system we've never seen or heard of before and none of the characters are connected to is important, and how Ben Solo was turned to the Dark Side...all of that was only explained in supplementary materials.
• Like Return of the Jedi before it, The Last Jedi fails to reveal the names of multiple places, people, and/or species in the film, such as Luke's home planet of Ahch-To, the bird-like Porgs that also inhabited the planet, and the Canto Bight smuggler that joined Finn & Rose during their side-quest, DJ. These pieces of information were all included in pre-release reference/tie-in material however, like Episode 6 listed above.
• The opening crawl of The Rise of Skywalker references a mysterious broadcast from Emperor Palpatine, which confuses all who listen to it and whose origin is unknown. The only place to hear the actual broadcast isn't in the film itself, but in... a cross-promotional marketing event that was held in Fortnite (It was also included in the novelization). Complete with unique dialogue by Ian McDiarmid.
  • Similarly, all of the details as to how Palpatine came Back from the Dead, who his legions of followers are, how they constructed their massive fleet of Star Destroyers, how exactly Snoke factors into everything and who Palpatine's "son" that sired Rey is are all presented in the film's novelization and Visual Dictionary but absent from the film itself.

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