Newer Than They Think: The story is well known and often appears in fairy-tale collections, which makes people tend to assume that, like most fairy tales, it has medieval or early modern origins. In fact, it was an original story written in 1840 — still old, but not as old as people think.
Fridge Brilliance: In an attempt to gain access to Practical Pig's house, the wolf disguises himself as a Jewish peddler. Since meat from a pig is treif (not kosher), what better way to trick pigs into thinking you're not going to eat them? Note that this only applies to the original cut, as later prints removed the Jewish aspects of the wolf's disguise.
Growing the Beard: Previously, cartoons had little story and focused more on surreal, often repetitive imagery for its own sake. This was the first animated short to not only have a linear plot but whose characters each had a distinct personality, two things that Disney and, indeed, most mainstream animation studios would focus on in the coming era. Amusingly, one New York theater took this to its literal extreme when it kept the short playing for so many weeks that they put up a sign saying "You've kept us here so long, we're growing beards!" complete with illustrations of the Three Little Pigs with real beards put on them. And they deliberately made the beards longer as time went by.
Nightmare Fuel: The Big Bad Wolf is a pretty comical type of villain, but in the 1958 Disney Records audio remake, he's given a very eerie and menacing voice and growl. It doesn't help that when it was used on the read-along book-and-audio adaptations of the cartoons, the illustrations (taken from the 1948 Little Golden Book adaptation) depicted the wolf as a freaky Off-Model dark-furred version with glowing yellow eyes and gleaming sharp fangs (as shown in the above link), itself a Palette Swap of Brer Fox.
Also Practical Pig's inventions: first off is the "Wolf Pacifier" from Three Little Wolves and the second one is the Lie Detector from The Practical Pig. While the first one is quite brutal-looking from the get-go, the second one actually has you hear the Wolf screaming throughout.
Unintentionally Unsympathetic: One possible reason why the sequels failed was that the pigs got Flanderized to the point where none of them were likeable anymore; Fifer and Fiddler became Too Dumb to Live and would constantly laugh off Practical's warnings while teasing and pranking him for no reason, while Practical turned into a preachy and self-righteous Killjoy who never stopped scowling and only stopped working in order to tell the other two off. He also started displaying a rather sadistic streak in dealing with both the Wolf and his brothers.
Awesome Music: A lot of the original music made for the play is absurdly catchy. In particular the opener - Pipo and Pepe singing about their peculiar butchery shop, as well as The Song Before the Storm sung by Pipo (in the wolf disguise) about blowing away the houses of the pigs.
, he's given a very eerie and menacing voice and growl. It doesn't help that when it was used on the read-along book-and-audio adaptations of the cartoons, the illustrations (taken from the 1948 Little Golden Book adaptation) depicted the wolf as a freaky Off-Model dark-furred version with glowing yellow eyes and gleaming sharp fangs (as shown in the above link), itself a Palette Swap of Brer Fox.