Star Wars Legends was infamous for its continuity snarls and errors. The continuity didn't have any kind of central planning until roughly the Turn of the Millennium (almost ten years into its existence), which was compounded by the fact that George Lucas didn't consider it part of his main universe to begin with nor care overmuch whether he contradicted it. In particular, material published prior to the prequel trilogy (e.g. most of the Bantam Spectra-published novels) generally assumed that the Clone Wars had been a separate conflict from the Jedi Purge and had taken place roughly forty years ago instead of twenty. The prequel Jedi practicing a Vow of Celibacy also caused a lot of confusion in various preexisting characters' backstories.
- Anyone who listens to the Star Wars Radio Dramas can't help but notice that Han shoots first and does not meet Jabba on Tatooine. These were two of the more infamous changes made by Lucas when he Re-Cut the 1977 film for re-release.
- One of the biggest snarls was "who stole the Death Star plans?" This was due to the fact that it was such a pivotal and easy story to cover (there's a reason Rogue One exists) that something like six or seven different stories were about the theft of the plans. Eventually, it was declared that pretty much everyone involved found bits and pieces of the plans, and the data R2 carried was basically all the assembled schematics that people had managed to scrape together. One official article jokingly noted "if you had to throw a dinner party and invite everyone who had ever stolen the Death Star plans, you'd be surprised at how many place settings you'd have to worry about."
- One of the simpler examples of this snarling; if you take the Original Trilogy and the EU as a whole, then it seems like Boba Fett manages to fall into the Sarlacc no less than three times: both the novel Tales of the Bounty Hunters and the comic "Boba Fett and the Jawas of Doom" start with Boba escaping from the Sarlacc's guts, but with completely different results. In the former, Boba is found and nursed back to health by Dengar,note while in the latter, he is found and temporarily enslaved by Jawas, only to end up plunging back into the Sarlacc's mouth again at the comic's end.
- Tales of the Bounty Hunters: Five regarding "The Last One Standing: The Tale of Boba Fett".
- Fett disbelieves in the Force here. Other material has him well aware that it's real (he experiences its effects himself). It also seems hard to believe he could be around Darth Vader that often without him demonstrating it (probably on some underling).
- His tale also says spice was illegal, while other books say it's just highly restricted (thus the smuggling of it).
- Fett is also stated to be a member of the Bounty Hunters Guild here, while other depictions are insistent that he's firmly independent. Indeed, The Bounty Hunter Wars has its plot start on him having to be bribed into joining as part of a scheme against them. However, this might be harmonized since the events of Tales where this is mentioned take place later than the other material when he's independent (though the guild's destroyed in The Bounty Hunter Wars, perhaps it was re-established later).
- Fett reflects he's never even held a woman, while later material establishes that he was married and had fathered a child.
- Fett is established to have been born with the name Jaster Mereel and is shown being punished for murder. His entire backstory was retconned by Attack of the Clones and "Jaster Mereel" became a different person (a mentor of his father whose name Fett used as an alias).
- The Courtship of Princess Leia:
- Luke believes sixteen is "too young to learn the ways of the Jedi". This in spite of the fact that Yoda says Luke is too old to be trained at twenty-two in The Empire Strikes Back. The prequel trilogy films showed children were mostly trained from childhood to be Jedi, with the Jedi High Council considering nine-year-old Anakin too old to be trained; however, material set in the Old Republic showed the Jedi sometimes being perfectly willing to train adults.
- The book has Luke say droids too are living beings, and can be sensed through the Force, while most Legends material had the opposite view.
- The Han Solo Trilogy:
- Han can't remember who his parents are or what happened to them here. Tales of the Bounty Hunters has him briefly muse about whether they would be proud of him, with every indication he remembers them, and says they died early in his life.
- Spice was also stated as illegal there, though in these books it isn't, but the legal price is so high it's often smuggled for profit on the black market.
- Bria, while undercover in the Imperial forces on Corellia, mentally reflects how the Empire is expanding its presence there and worries about them sending a Moff. However, in other Legends material its stated the Corellian system did have a Moff, Fliry Vorru, who had been Corellia's governor since the Republic era and received this post after the Empire was declared. The Corellian Trilogy states that before being annexed by the New Republic, the Corellian sector was ruled by a pro-Imperial head of state called the Diktat, but this isn't mentioned in these books.
- Knights of the Old Republic: Jolee Bindo, in his youth, married a woman named Nayama in secret due to the Jedi prohibition on romance and in the sequel Darth Traya confesses to having been exiled from The Order after they found out she became a mother. This was during the Great Sith War, and he also talks about meeting Nomi Sunrider. The problem? The Jedi in Tales of the Jedi have no prohibition on marriage (an assumption from before the prequel trilogy came out). Nomi was openly married to a Jedi, had a child by him who later became a Jedi, and was openly dating another Jedi during the same time period that Jolee's marriage with Nayama was frowned upon.
- The Ubese were a race of Scary Dogmatic Aliens who developed Fantastic Racism towards the rest of the galaxy after The Republic and Jedi accidentally destroyed their homeworlds. Knights of the Old Republic II: The Sith Lords established the event as having taken place prior to the game's beginning in 3951 BBY, however The New Essential Chronology and The Essential Atlas reference books contradict this and place the event over 2000 years later.
- The infamous question of how many clones there are—the films imply the Republic had a couple million units and R.A. Salvatore's novelization confirmed that a "unit" meant a single clone, but considering that those same films suggest that the Separatists had tens of thousands of planets at their disposal, it was a very hard sell. Because of this, you had writers tug-of-warring between "there were definitely just three million or so" to "no, a 'unit' does not mean a single clone, the actual army was orders of magnitude bigger." One writer would declare that individual clones were more like elite special ops and most of the fighting was done by militias or local forces, and then another would show the Republic tossing all-clone armies in the hundreds of thousands (with no militia in sight) into a pitched battle and taking staggering losses.
- While the Clone Wars era was generally treated as off-limits, the pre-prequel EU had no problem sneaking in things mentioned to be from that era: for instance, ships like the Victory Star Destroyer and the Z-95 Headhunter were mentioned to be the Clone Wars equivalents to more modern tech, and The Thrawn Trilogy featured "cloning cylinders" that were stated to have been used in the wars and implied to have been used by the Republic's enemy. Then the prequels came out, and ignored almost all these details; the frontline Star Destroyers were the Venator and Acclamator, the ancestral X-Wing was the ARC-170, and the clones fought for the Republic and were created in an entirely different fashion. Later writers had to do some Canon Welding to explain where all the prequel-era tech had gone to and why the EU tech seemed to be missing: for example, the Republic Commando Series explained that the Spaarti cylinders used by Thrawn were used to create a "surge" of new clone troopers late in the Clone Wars to bulk up the army ahead of Palpatine's coup.
- Several of the pre-prequel EU works said or strongly implied that the Clone Wars involved clones fighting against the Jedi and/or the Republic. The Thrawn Trilogy outright mentions some "Clone Masters", who created clones to fight the Republic. Timothy Zahn would later fix this by saying the Clone Masters were rogue Kaminoan cloners who attempted a coup against The Empire, which is shown in Star Wars: Battlefront II.
- Ben Skywalker's eyes are described as grey after he's born in New Jedi Order, then as blue in the Dark Nest Trilogy, then the second book of Fate of the Jedi says they're green, only for the fifth book to describe them as blue once again.
- The prequels made a mess of Michael Stackpole's work in the X-Wing Series and I, Jedi.
- The Halcyon-Horn family tree requires that Valin Halcyon/Hal Horn have been an adult at the time of the Jedi Purge and that he was already married with an infant son, Corran; his father Nejaa was also his Jedi Master. Except there's that whole pesky thing about the prequel Jedi Order banning marriage. Two different retcons were attempted here: some material stated that the Corellian "Green Jedi" tended to play by their own rules (e.g. Star Wars: The Old Republic portrays them more as coreligionists of the mainstream Jedi Order than properly part of it, complete with their own independent Jedi Council), while the novel Jedi Trial depicts Master Nejaa Halcyon supervising Anakin Skywalker's graduation to the rank of Knight, and finding a Commonality Connection between their respective Secret Relationships.
- Who is "Desertwind", the third Jedi in Ylenic It'Kla's recollection of Nejaa's death? Stackpole strongly indicated this had been Obi-Wan Kenobi (under the assumption that Kenobi was from Tatooine, which was jossed by The Phantom Menace only a year later), but he could also be Anakin Skywalker or somebody completely unrelated such as A'Sharad Hett (first introduced a year after the novel came out). Further muddying the waters, the mission in question supposedly took place between the Clone Wars and the Jedi Purge, which is impossible given the timeline of Revenge of the Sith. The Short Story "Lone Wolf A Tale Of Obi Wan And Luke" by Abel G. Peña confirms it was Kenobi, but it wasn't published until after the changeover to Disney canon so its canonicity in Legends is questionable.
- The first book in Young Jedi Knights mentions that Anakin Solo would be going to Luke's Jedi Academy soon and can't wait to come join his elder siblings in Jedi training, as if he hasn't attended yet. Junior Jedi Knights, which was released later in the same year but set before Young Jedi Knights, showed that Anakin already studied at the academy.
- A big one was the political makeup of the galaxy, especially the Vestigial Empire, post-Endor.
- The Courtship of Princess Leia (1994) is set a year prior to The Thrawn Trilogy (1991), but implies the Empire has now broken up into many independent warlords ruling fiefdoms in the galaxy. The Thrawn Trilogy meanwhile said nothing of the kind, having it that the Empire had simply shrunken in size over the five years after Palpatine's death at Endor. This was harmonized later by saying both were true: a number of warlords broke off to form their own fiefdoms, while the Empire proper also remained (Thrawn controlled this portion, having returned from the Unknown Regions to take it over after Imperial Intelligence Director Ysanne Isard was killed in the Bacta War), and their holdings were then reintegrated after Daala had the last warlords gassed at a meeting, then Pellaeon took power.
- The Shadow Academy arc in Young Jedi Knights (1995-1996) had an Imperial Remnant faction called the Second Imperium as Brakiss's backers. This was contradicted by Darksaber (1995) by the same author, which showed the remaining Imperial Remnant warlords being killed off and their fiefdoms seized and reunified by Admirals Natasi Daala and Gilad Pellaeon eleven years earlier, and then by Timothy Zahn's The Hand of Thrawn (1997-1998), which ends with the Republic and the Empire signing a peace treaty and normalizing relations four years before YJK. The official explanation is that the Second Imperium was a Renegade Splinter Faction that refused to accept the peace.
- Black Fleet Crisis (May-December 1996): Michael P Kube Mc Dowell very much did his own thing with this trilogy, causing a lot of contradictions right down to details of Coruscant's geography.
- The novels state that there was no organized Imperial Remnant at all anymore, four In-Universe years after Darksaber (1995) reunified it.
- They also stated that the New Republic has officially been in peacetime long enough they put up an "X Days Since There Was War" clock in its Senate building (it's taken down when the Republic declares war on the Duskhan League in book three). The Essential Chronology (2000) directly contradicted this, stating that Admiral Pellaeon's Empire was still skirmishing with the Republic throughout the timeframe of this trilogy (though major hostilities had ceased because the Republic was winning most of them from its sheer size relative to what was left of the Empire).
- Ditto the statement that the New Republic has nothing the size of the Yevetha-controlled super star destroyer Intimidator/Pride of Yevetha that can face it in a Standard Starship Scuffle, having preferred a fleet of smaller and more flexible ships (though the point ends up being moot when Imperial POWs enslaved by the Yevetha stage an uprising and steal it). X-Wing: The Bacta War (1997), set nine years earlier, ended with the New Republic's capture of the Executor-class SSD Lusankya. According to The Essential Chronology, they subsequently used it against Pellaeon in the Orinda Campaign—ironically first mentioned in Before the Storm itself—as a hard counter to Pellaeon's own SSD Reaper, and hung onto it through the halfway point of New Jedi Order.
- These novels attempt to show some technological progress in the galaxy, with the New Republic Defense Force having phased out its Y-Wings and B-Wings in favor of the new K-Wing tactical bomber, and even Luke has traded his X-Wing in on an E-Wing. Several novels set chronologically later contradict this trend because Status Quo Is God, though the X-Wings are excused by Incom having developed upgraded models.
- Kevin J. Anderson deliberately only named six of Luke Skywalker's "Original Twelve" Jedi candidates in the Jedi Academy Trilogy to make room for other authors to introduce their own. Three of the other six were solidly established by later works: Brakiss in Young Jedi Knights, Corran Horn in I, Jedi, and Kyle Katarn in The Essential Chronology. Outside of published works, canon master Leland Chee identified Madurrin, who first appeared in Destiny's Way, as the fourth. There are at least four competing candidates for the last two slots, the major ones being Havet Storm (Jedi Knight II: Jedi Outcast), Keyan Farlander (from a Star Wars Insider #57 article), Nichos Marr (Children of the Jedi), or Harlan (The Jedi Academy Sourcebook).
- Star Wars: The Clone Wars seasons 1-6 are still considered part of the EU by Lucasfilms, but it at the time was notorious for contradicting almost the entirety of the Clone Wars Multi-Media Project. Many characters die entirely different ways such as Evan Piell, some characters are revived despite dying in the CWMMP or Episode II such as Eeth Koth, Grievous is depicted as having always been as he was in Episode III rather than that being the product of his encounter with Mace Windu, characters such as Quinlan Voss are changed entirely personality-wise, Anakin's knighting is very early in the war, Ventress' fate is entirely different, the Nightsisters and Dathomir are depicted differently with the former being wiped out by Grievous long before The Courtship of Princess Leia, Maul is still alive, etc. This is exactly what led to the canon tiers.
- Why did the clone troopers obey Order 66? A strict reading of the films had Lama Su in Attack of the Clones stating they were genetically predisposed to obey orders that appear to come from a valid source, which was basically the explanation that Matt Stover's Revenge of the Sith novelization used (which also explained why so few Jedi sensed it coming: the clones didn't have any malice towards the Jedi or think the order was unusual in any way). However, since a number of Jedi had already been established to survive the Jedi Purge, some Legends stories showed clone troopers questioning or openly disobeying the command. Other stories, most famously the Republic Commando Series, suggested that a lot of clones disliked or hated the Jedi for various reasons (such as their complicity in the clones' enslavement) and saw Order 66 as a chance to legally get even. All of these competing explanations were ultimately Jossed by season 6 of Star Wars: The Clone Wars, which established that the primary reason was that the order was a trigger for Restraining Bolts implanted in the clones' brains, meaning that they couldn't have disobeyed even if they wanted to (the few clones shown disobeying the command in the Disney-era season 7 had previously had theirs removed).
- The Revenge of the Sith novelization rewrites enough dialogue and scenes it's practically an Alternate Continuity to its own canonical film. Also, while it frequently references other EU books, it gets some details wrong. In one scene, Palpatine attempts to sow doubt about Darth Sidious's existence in Anakin, suggesting there is no evidence of his existence and he could be a fabrication, and Anakin doesn't bother to bring up the holographic recording he and Obi-Wan found of Sidious in the preceding book, Labyrinth of Evil (released three months earlier). The opening chapters of the book also suggest that the Republic is losing the war when the previous book (and the film) suggested the exact opposite. Palpatine's "Not Illegal" Justification about being a Sith in the novel was in turn contradicted the next year by Darth Bane: Path of Destruction, which stated that the Republic had in fact outlawed the Sith religion and ideology circa Knights of the Old Republic.
