Author Existence Failure: Poor, poor Mary Wickes, Laverne's voice actress. This was her final film role as she died of cancer during production and had to be replaced by a stand in, although thankfully only for a few lines. Fortunately, that stand-in is sound-alike Jane Withers, who took over the role in much-maligned DTV sequel.
Genius Bonus: The actual, present day Notre Dame has two pillars missing, a damaged gargoyle, and a broken doorknob. Not only does this damage happen in the climax, it's all significant in some way.
Also, the background singing in Frollo's scenes throughout the film has several layers of meaning:
'Kyrie Eleison', a refrain which is repeated throughout the film, means 'Lord have Mercy'...appropriate.
The chanting when Frollo is chasing Quasimodo's mother through Paris comes from a Gregorian chant called the Dies Irae - Day of Wrath - and includes a phrase that roughly means 'Beware the coming of the judge.' Again, appropriate.
And, during Hellfire, the shadowy figures that torment Frollo in his madness chant 'Mea Culpa' - 'Through my Fault' - something which Frollo constantly denies.
Quasimodo's climatic scene (being chained to the pillars of the church, then tearing them down in rebellion) is lifted directly from the story of Samson in the Bible.
Reversed in Sweden, in the dub the same guy voices Ratcliffe and Frollo.
Mean Character, Nice Actor: In an interview for Disney Adventures that was published right around the time that the movie was released, Tony Jay made it a point to say that he was actually a very nice man in Real Life, despite continually playing villainous roles (and with Frollo being one of his darker ones).
Non-Singing Voice : Averted; with the exception of Esmeralda, every actor does their own singing. Tom Hulce, Quasimodo's voice actor, wanted to be a singer when he was younger.
What Could Have Been: Phoebus's speech rallying citizens to rebel against Frollo during the climax of the movie was originally said by Clopin, but the directors/producers felt that Phoebus needed to be more involved in the uprising.
The other films
Fake Nationality: In the 1939 version, the French characters are played by British and American actors. In the 1956 version, most actors are French, but Esmeralda is played by the Italian Gina Lollobrigida and Quasimodo by the Mexican American Anthony Quinn.