The Gremlins: (Based on Roald Dahl's book. Questions of whether plane sabotaging creatures could be made sympathetic and development running late into the war leading to a cancellation due to possibly becoming dated. Some Gremlins would later appear in the 2010 video game Epic Mickey.)
Fraidy Cat (a homage to the work of Alfred Hitchcock focused around house pets, was supposed to be Ron Clement's and John Muskers' next film after Treasure Planet)
Wild Life (a Pygmalion-type story about a nightclub recruiting a singing zoo elephant to hype into the next big thing to discredit a critic, cancelled due to concerns about more mature content)
My Peoples (Loose Applachian set adaptation of The Canterville Ghost, cancelled due to the closure of the Florida studio, which was the only one making the movie)
Fantasia 2006 (due to shifting management; several shorts were completed and released separately)
Mort (Disney couldn't get the adaptation rights, which were sold as one large package rather than individually)
Sequels were also planned for films such as The Jungle Book and Bambi during earlier phases, though didn't get past early production stages (allegedly due to Walt not being a fan of sequels). Actual follow ups were made much later on, though are not made part of Disney canon.
In their line of Direct-to-Video sequels, Disney had plans to make Dumbo 2, The Aristocats 2, and The Jungle Book 3. The first was shelved for a while (even though it was promoted on the 2001 DVD of Dumbo). All three of these projects were cancelled under order of John Lasseter.
On a similar note, recently and not without backlash, Tangled and Frozen received their title changes from Rapunzel and The Snow Queen respectively as well as a whole new marketing strategy to make sure their more princess-central films can still net young males. Notably this came after the presumed failings of The Princess and the Frog. Though admittedly it was for the better as far as Frozen is concerned, seeing as the title fits the setting and theme a lot more than "The Snow Queen" does (it was also initially going to be an adaptation of The Snow Queen, but ended up being inspired by it instead).
Cover Version: DisneyMania, for a number of hits from movie soundtracks. In some cases, song covers are included in DVD sets. It's also fairly common for a contemporary artist to cover a song from a movie.
Frozen is a major, major contender for this, despite having a bodycount of only 2 minor characters (King Agdar and Queen Idun), and the villains punished justly without death. The film features childhood trauma, dead parents, murderous noblemen, a comic relief character that spends the movie dreaming about what would kill him, and the entire cast nearly dying in a massive snowstorm near the end.
Deconstruction: This along with subversions have become a growing trait of the newer films, what with Disney having been around for so long that telling something completely and entirely new gets understandably difficult. As such, they've begun taking what's been done and ...toying with it. Heavily prevalent in the three most recent princess-centric films: The Princess and the Frog, Tangled, and Frozen.
Denser and Wackier: The tone of the films constantly vary, the majority of films made in the 1960s and early 1970s use a much more offbeat and wacky tone than usual however, with less drama and more comedic and sympathetic villains. The Rescuers began the return to more darker and earnest story telling (albeit with Disney's usual whimsy).
Disney Princess: A title given to the lead female character in several films in the canon, as a big marketing ploy for girls that more or less took on a life of its own.
There's more than ten, there's just ten "official" princesses in the product line. Princesses like Tiger Lily, Eilonwy, and Kida aren't included in the line, despite being princesses by blood, unlike the aforementioned exceptions.
The High Queen: At the end of Atlantis: The Lost Empire, where its princess becomes Queen by the end of the movie. Frozen also features one of the two princess characters become a queen by the beginning of the movie and be good.
None of the villains in Pinocchioare ever punished — Pinocchio just escapes from them. The loss of just one boy presumably not being significant, it can even be said that the Coachman won as far as his scheme went.
Disney Villains who play it straight: click here The Evil Queen, Maleficent, possibly Madame Medusa, The Horned King, Ratigan, Sykes, Ursula, Percival McLeach, Gaston, Scar, Frollo, Shan-Yu, Clayton, The Carnotaurs, Rourke, Helga, Scroop, Dr. Facilier, Mother Gothel, King Candy.
Disney Villains who avert it (Karma Houdini examples marked with *): click here Honest John and Gideon*, Stromboli*, the Coachman*, Monstro, Chernabog*, Man*, The Wolf, Willie the Giant, Mr. Winky, The Headless Horseman*, Lady Tremaine* (she got her karma in Cinderella III, though), Queen of Hearts*, Captain Hook, Si and Am*, Cruella, Madam Mim, Shere Khan (until the sequel came around), Edgar, Prince John, Jafar (again, until the sequel), Governor Ratcliffe, Hades, Yzma, Gantu, Alameda Slim, Bowler Hat Guy, The Backson, Prince Hans, The Duke of Wesselton.
Knight of Cerebus: Though some may still be somewhat comedic, a lot of villains have a very menacing tone (especially in the earliest examples) and are responsible for a lot of Mood Whiplash away from Disney's usual whimsy. See this page for their rather haunting effect on many audiences.
Limited Special Collector's Ultimate Edition: The "Black Diamond" Classics, the Masterpiece Collection, the Gold Collection, the Platinum Editions and the Diamond Editions, all of these sets being released in a wide variety of home video formats, with VHS, DVD, Blu-ray and LaserDisc being the most popular. And of course, the Disney Vault that these all get shoved into if you don't buy them now!
Special mention goes to the Masterpiece Collection, which included every VHS release at the time that was part of the Canon, including the stuff nobody remembers (like the compilation films) and the brand-new movies. From Tarzan on, they just put "Walt Disney Pictures Presents" on new releases.
Only a handful Disney movies subvert or avert this trope. In some examples, John Smith (explorer), Taran (pigkeeper/peasant) and all main characters of The Hunchback of Notre Dame (soldier, son of a gypsy, gypsy performer) are self made heroes.
Non-Human Sidekick: Most of the main characters and/or their love interests have one, as do some villains.
Strictly Formula: During the 1990s, Disney had a very succesful run from 1989 till 1994, but after that they were often accused of enforcing this trope. Rebellious princesses who want to marry for love, heroines looking for something beyond what they know, bumbling or fantasy-forbidding fathers, bad guys falling off great heights. Pocahontas especially was accused of adhering to Disney formula, which admittedly is not entirely untrue. Ironically though, the problem seems to have been that all these movies came out in succession, as every single movie of the Disney Renaissance has been Vindicated by History and is now well-loved (some more than others: Pocahontas is still not thought of as a great movie, and The Rescuers Down Under has gained a cult following but isn't anywhere near mainstream).
"Human Again" from Beauty and the Beast and "Morning Report" from The Lion King were un-needed additions to their respective films, since the movies didn't have them originally. They aren't terrible songs, nor completely irrelevant (they're both in the stage versions of the respective movies, too). Neither of them exactly advanced the plot or provided much if any character development, but both were intended to be in the original production (and are in the Special Editions).
Time Skip: Several movies in the canon started adopting this measure beginning in the Disney Renaissance period (though it had been used since the earliest movies), and continuing to this day. It got really egregious during the height of the Disney Renaissance period, when films like Hercules and Tarzan would have two or more timeskips within the expanse of a 3-minute song.
The End: Prior to 1985's The Black Cauldron, every Disney animated film (as well as most live-action films and theatrical shorts) ended with a screen saying "The End", and below that, "A Walt Disney Production" (during Walt's lifetime) or "Walt Disney Productions" (after his death). The Great Mouse Detective (1986) and Aladdin (1992) also had "The End" screens, without the Walt Disney credit.
The Verse: Possibly with all the cameos and easter eggs and what not.
Tangled and Frozen are all but explicitly confirmed to exist in the same universe, with Fanon generally accepting Rapunzel, Anna, and Elsa to be cousins by way of their respective mothers being sisters. A common theory also places The Little Mermaid in this same universe with the sunken ship Ariel explores at the beginning being the same one that carried the king and queen of Arendellenote Traveling from Norway to, presumably Rapunzel and Eugene's wedding in Germany, would mean the ship would go down off the coast of Denmark, where Mermaid is set.