Development Hell: Was in the works for almost all of the 1950s with production starting in 1951 and being released in 1959. In that time, it became a financial behemoth which didn't make its cost back despite being the second-highest grossing movie of the year. Sleeping Beauty Castle at Disneyland had visitors walking past a set of dioramas of scenes from the movie in 1957, and the movie was still two years off.
Genre-Killer: The film's failure to earn back its exorbitant budget resulted in this twofold: it was not only the last animated film based on a fairy tale that Disney would make until The Little Mermaid in 1989, it also ended Disney's second run of lavish, expensive animated features that had been restarted with Cinderella in 1950; this inadvertently began The Dark Age of Animation, as Disney was the last studio in Hollywood who was willing to spend money on full animation.
The original storyline had Aurora grow up at the palace, like in the original fairy tale. She and Philip would have met after she snuck out to a local fair, disguised as a servant girl.
Diablo was originally a vulture who spoke with an anachronistic Brooklyn accent.
An early treatment has Aurora prick her finger not because Maleficent hypnotizes her, but rather because Maleficent convinces her that touching the spindle would grant her strongest wish (similar to how Snow White bit the poison apple after the Witch called it, "a magic wishing apple".).
The Three Good Fairies were originally meant to have powers associated with their names, but this was scrapped during production. Flora's idea of turning Aurora into a flower is a leftover from this part of development.