Accidental Aesop: At the beginning of the film, Pongo was dismissive of an Afghan hound and a poodle as "too strange" and "too fancy", respectively. But during the Twilight Bark, these two dogs show up again, eagerly passing on the message to help him find his lost pups. What's true for dogs is true for people, too: Never judge somebody's character from their appearance, their ethnicity or their class. There is good and bad to be found in all stripes, and someone you might dismiss because you tarred them with the same brush could surprise you.
Adaptation Displacement: That's right, there was a book. There was a book called The Hundred and One Dalmatians (without the "one" at the beginning). People only familiar with the story from the movie might be shocked to find out that Perdita was called 'Missis' (while there was a Perdita in the novel, she was a different character), Cruella had a husband and a pet cat, and a subplot contained Perdita's lost love who went missing. The book had a sequel too, but both the animated and live action sequels were original stories.
Broken Base: Disney buffs can't decide if this film is the start of the Dark Age for the studio. On the one hand, it marked a huge downgrade from the animation of the previous film Sleeping Beauty thanks to the studio using xerography to photocopy the cels rather than hand-inking them to save money. On the other hand it was still one of the highest grossing Disney films, so some regard it as the final great Disney film before the Dark Age (although some give that to The Jungle Book (1967) — the last completed film Walt worked on).
Many people who haven't seen the movie assume it's about a pair of Dalmatians who have 99 puppies. In reality, Pongo and Perdita only have 15; they adopted the rest after saving them from Cruella.
No, Cruella doesn't have some murderous hatred of Dalmatians. She just thinks their fur would look good as a coat, that's all.
Do Not Do This Cool Thing: Writing a best-selling song about someone you don't like and explicitly naming them in the lyrics, is a good way to get sued in Court for libel and slander.
Hollywood Homely: When Pongo is scouting out a mate for Roger (and himself), the first woman to walk by is a gangly brunette in glasses and a beret, carrying an easel and walking an Afghan hound. Pongo's quick to dismiss the pair, but they weren't all that bad-looking, and the woman probably wouldn't have been the worst match for Roger, especially considering they're both artists.
Jerkass Woobie: Horace and Jasper could qualify considering they have to endure the berating of their Bad Boss Cruella.
Love to Hate: Cruella—aside from the Dalmatian puppies, Cruella's easily the most popular/iconic character from the movie.
Mandela Effect: Some people remember Cruella De Vil's name being spelled as "Cruella De Ville" or something similar. While the name is obviously a pun for "cruel devil", a lot of people remember it as being more creative than just putting a space in the word "devil".
"Blast this pen! BLAST THIS WRETCHED, WRETCHED PEN!"
In Israel, kids often call Cruella ‘debil’ (a word borrowed from French débil via Russian meaning ‘dumbass’).
Misaimed Fandom: Many fur fans actually like Cruella, especially the animated version, for her huge fox coat. And a lot of the mentions of fur, like sleeping between ermine sheets in the book, often just seem like a sybaritic Pretty in Mink.
Money-Making Shot: Cruella in her car, chasing after the van carrying the puppies as her hair flies in the wind and her eyes go bloodshot. Easily one of the most remembered moments, and used in lots of promotion to sell her determination.
Moral Event Horizon: Cruella, Jasper and Horace are already established as cruel for their part in stealing the puppies and even if they didn't know that they were as sapient as them, the fact still remains that they are willing to murder dogs because of some petty desires. And then they try to run the truck off the road and kill the human driver just to catch the puppies (and if it wasn't for Horace's clumsiness they would have succeeded) sealing the fact that they have no respect for life in general, be it human or animal.
Older Than They Think: Cruella's iconic Evil Laugh was actually a trademark of actress Betty Lou Gerson, who was using it a while before this film. This even allowed for an impressive Mythology Gag in Cruella where the new version models her laugh on a Gerson film.
One-Scene Wonder: The four cows only appear in the film for a few minutes to feed the puppies, but they're iconic characters and arguably feature the film's Signature Scene.
The Twilight Bark sequence lasts five minutes and is basically characters repeating information the audience already knows.
The scenes of the Dalmatians wandering the frozen countryside are mostly this too, although they do at least allow the puppies to interact with their parents.
Sampled Up: The famously catchy "Cruella de Vil" may intentionally sample the chorus line of Thelonious Monk's "Bolivar Blues", which got its first album release in 1957.
They Wasted a Perfectly Good Character: With such fun side characters like Tibbs, Colonel, Nanny, Horace and Jasper - the puppies themselves are pretty underdeveloped. They're pretty much Living MacGuffin characters with only a couple of traits to distinguish them. Compared to the original novel, the puppies in the movie interact and banter with each other far less than they do in the book. Notably the spin-off cartoon would flesh them out a lot more, as well as characterize the main pups more in line with their book counterparts.
While the profession of writing songs for other artists to sing was quite thriving for decades, it would quickly start to be rendered obsolete just two years after the film's release thanks to the emergence of The Beatles and their popularization of artists writing their own songs, which remains the default model today. Consequently, Roger's dream of becoming a professional songwriter seems much less immediately relatable to a modern audience than it did in 1961.
What's My Crime? is a parody of the then-airing game show What's My Line?. This is a reference that everyone would have gotten in 1961, but it's decidedly more obscure now except in the game show community.
Values Dissonance: While Perdita's giving birth to her and Pongo's original fifteen puppies, Anita and Nanny are helping her while Pongo and Roger are waiting in another room, behind a closed door. When the movie was produced and released, it was typically frowned upon for men to be present when their wives/female partners were in labor, and men were basically flat-out banned from delivery rooms. Decades later, however, the biological father is more often than not expected to accompany the biological mother during the child's birth (provided that they're still romantically involved).
Viewer Gender Confusion: Pepper gets one speaking line during the entire film and her voice led many people to believe she was a boy.
Visual Effects of Awesome: All of the cars! Looks like CGI, right? Actually, they're wooden models with hard black lines painted on their edges, photographed moving in real time with every frame then blown up and xeroxed onto animation cels. Despite all this, they haven't aged a day!
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