At the beginning of The Adventures of Tintin, a painter paints a portrait of Tintin. The painting turns out to be his design from the comics! And if you look closely in the background, you can see that the painter has done paintings of the other characters from the comics too. What's even better is that the painter is a Creator Cameo of Hergé.
Genie asks "You've just won the heart of the princess. What are you going to do next?" In ads, celebrities would answer such questions with "I'm going to Disneyland!" As he asks, the soundtrack plays a few notes from the beginning of "When You Wish Upon a Star", the famous song from Disney's Pinocchio that was at the time used as the anthem for the Disney theme parks.
Also, perhaps, the start of a Brick Joke: at the end of the film, after Genie is released, he is seen wearing a touristy Hawaiian shirt and a Goofy hat.
The Disney FairiesTinker Bell movie opens with a paraphrase of the origin of fairies in Peter and Wendy, and the sequence of Tink being created seems to be set (between the baby's laugh, and her arrival in Pixie Hollow) in Kensington Gardens, location of J. M. Barrie's Peter Pan in Kensington Gardens (which eventually became the story we're familiar with), and current site of a statue of Peter.
In Frozen II, Young Agnarr says he is reading a book by "some Danish author", clearly a reference to Hans Christian Andersen, who wrote "The Snow Queen", which served as the inspiration for the franchise. In addition, the image on the book resembles one of the posters of The Little Mermaid.
It has several literal Mythology Gags referencing the 12 Labors of Hercules/Herakles — like the lion's skin he wears when posing for a portrait, or when he breaks into Hades' private chambers while riding Cerberus. The series has even more, like when he applies for his "hero's license" and finds out he's 12 deeds short.
Double bonus — that lion skin is actually Scar. About whom Zazu said "He'd make a very handsome throw-rug."
How to Train Your Dragon: The Hidden World: Near the end of the movie when Hiccup and Astrid take their children to visit the Hidden World, Hiccup's story references the opening monologue of the first How to Train Your Dragon book: "There were dragons once, when I was a boy..."
In The Lion King 1½, when Timon has to take care of Simba during the night, they are seen walking across the same log bridge seen during the Time Skip in the original movie. Upon the third instance of this, Timon even says, "We're going to get old walking across this thing."
In the same film, during the scene when Pumbaa pauses the movie to grab a snack, Timon hums "It's a Small World After All" to himself, possibly to reflect the scene between Zazu and Scar.
One of the fish in the "You're Welcome" Disney Acid Sequence resembles Flounder from The Little Mermaid (1989). Tamatoa's lair also resembles Ariel's grotto. And in The Stinger, the still overturned Tamatoa complains to the audience that they would help him if his name was Sebastian and he had a Jamaican accent. Moana was directed by Ron Clements and John Musker, the same people as TLM.
Flash the sloth from Zootopia appears in the Realm of Monsters.
While trying to control his shapeshifting after recovering his fish hook, Maui transforms into Sven the reindeer.
A Polynesian-style drawing of Wreck-It Ralph can be seen near the end of the credits.
Hogarth's surname, Hughes, is an homage to the original book's author, Ted Hughes.
The original book opens with the Giant shattering from falling off a cliff and his pieces reassembling themselves. He demonstrates this ability in the film when a train damages his hand. The final scene shows his body rebuilding itself in the arctic, much like he did in the beginning of Hughes' book.
The original book had a giant space dragon invade earth because it was provoked by the violent nature of warfare, with the world's armies launching a futile counterattack. This is a little similar to how the army assaults the alien threat of the Giant himself, who becomes a terrifying alien monster when they push him too far.
Flashpoint Batman flat out calls the group Cyborg is putting together a Suicide Squad.
Aquaman losing his right arm.
Flash first starts realizing he's in an alternate universe when he hears about the Elongated Kid (as opposed to Miss Alchemy in the comic), a superhero he's never heard of, being murdered. In the DCU that took place in the pre-Flashpoint continuity in the comics leading up to the event (Thawne did it).
Hal Jordan tells Aquaman's forces to "Beware my power, asshole!"
The movie opens with a Minor Kidroduction, showing the penguins as children in Antarctica and how they became lost at sea where they eventually end up in New York, much the same way Madagascar: Escape 2 Africa depicts this happening to Alex.
The main plot opens with a celebration of Private's 10th birthday and escalates from there; Marty's 10th birthday similarly motivates the opening act of Madagascar.
When locked in a cage, Skipper orders Rico to bust them out, which he does by coughing up a paperclip to pick the lock with. This action in the first movie is what inspired his stomach of holding abilities.
The Penguins meet a rival group known as the North Wind, who are comprised of northern animals. The penguins don't get along with them at all, aside from one of them having a crush on the female of the group. The idea that the Antarctic Penguins would be natural rivals of Arctic life but one of the penguins having a crush on one of them also comes up in Merry Madagascar.
King Julien's cameo in The Stinger uses an older design that would be out of date relative to the time the movie takes place, but matches how he appeared alongside the penguins in The Penguins of Madagascar cartoon.
In the seventh Pleasant Goat and Big Big Wolf film, Amazing Pleasant Goat, Super the penguin, upon initially meeting Weslie, decides to nickname him "0803". This is a reference to when the Pleasant Goat TV show started airing (August 3rd, 2005, or 8/03/05).
The Princess and the Frog: Back in The Lion King, Timon claims that stars are fireflies that got caught in that big bluish-black thing, and laughs at Pumbaa's suggestion that they're balls of gas burning millions of miles away. In The Princess and the Frog, another Disney film released over a decade later, the firefly Ray is in love with "Evangeline", a star that he believes to be a firefly. And later in the movie, a distraught Tiana quotes Pumbaa, telling Ray that Evangeline is really a ball of gas etc. etc. And at the very end of the movie Ray dies, but is seen to Ascend to a Higher Plane of Existence.... as a star, shining right next to Evangeline. So... it looks like Timon was right.
You can clearly see a teapot and cup almost identical to Mrs. Potts and Chip from Beauty and the Beast, when the monkeys are rocking out at the camp. (The only difference is a lack of eyes and mouth.)
The set returns in Kingdom Hearts' Deep Jungle level. Ironically the real Mrs. Potts appeared in the second game where Deep Jungle did not appear.
Also, later in the movie, when the gorillas hold Professor Porter upside-down, one of the many things that fall out of his pockets is a toy Little Brother from Disney's Mulan.
Another obscure Ride Cameo sneaks into Toy Story 2 when Tour Guide Barbie starts channeling the automated voice from the Matterhorn (quite audible from the line): "Remain seated please. Permanecer sentados por favor."
Trolls: At the start of the film, when the Bergens discover that all the Trolls have escaped from the tree, the wooden decoys look exactly like the classic Troll dolls. In fact, the earliest Troll dolls were made of wood.
The Pooh doll for the live-action opening of Winnie the Pooh (2011) was originally made for the first Pooh film Winnie the Pooh and the Honey Tree in 1966, but ended up being replaced by a different doll. It was finally used 45 years later.
A glimpse of some side characters gives us a weasel named Duke Weaselton, referencing back to a character mispronouncing the Duke of Weselton in Frozen. (When she confronts him at his pirate DVD shop, Judy mispronounces his name as "Weselton" and he corrects her, thus echoing and inverting the joke from Frozen.) They even share the same voice actor, Disney Animation regular Alan Tudyk.
When Judy confronts Chief Bogo wanting to be a real police officer, he bluntly tells her that "Life isn't some cartoon musical where you sing a little song and your insipid dreams magically come true. So, let it go."
At the climax, the deer mannequin that "savage" Nick mangles is recognizably Bambi.
There are some references to Robin Hood in terms of character choices. Most prominently, Nick is a Guile Hero of a criminal fox in green clothing, much like Robin Hood himself. There's also Mayor Lionheart, an anthropomophic lion sharing a name with the anthropomorphic lion version of Richard the Lionheart, but who also has wolves working for him much like Robin Hood's villain Prince John did. These aren't just convergent animal stereotypes, either: co-director Byron Howard was inspired to make Zootopia based on Robin Hood.