Awesome, Dear Boy: Why Angelina Jolie signed up for the role when she heard of the project, even though she was initially skeptical of whether or not they could make a feasible story. Same goes for Elle Fanning; she grew up watching Disney Princess movies and dressing up like them, so of course playing one (who also just happened to be one of her favorite princesses) in an actual film appealed to her.
Dawson Casting: Inverted. Aurora is 15/16, while Elle Fanning was 14 during filming. Compare that to the original film, where Aurora looked like she was in her 20s and was voiced by the just-under-30 Mary Costa.
Doing It for the Art: Elle Fanning re-watched the original animated movie to pick up Aurora's character tics, particularly scenes where Aurora walked through the woods. Sam Riley also studied ravens in order to get a feel for Diaval's character.
In the German dub, Diaval is voiced by Timmo Niesner, who commonly voices Elijah Wood characters (most famously Frodo).
The Other Marty: India Eisley (Eve from Underworld: Awakening) was originally cast as Young Maleficent, but she was replaced with Ella Purnell after Disney executives expressed displeasure with her performance.
Promoted Fangirls: Maleficent was Angelina Jolie's favorite Disney character growing up; meanwhile, Elle Fanning loved Aurora since she was a young girl. Both got their chance to play them with this film.
Real-Life Relative: The girl who plays the young Aurora is played by Jolie's daughter. This had to be invoked since she was the only child that didn't get scared when she saw Angelina in costume.
Two of her other children are nobles in the Christening scene at the beginning.
Recycled Script: A lot of the dialogue in the Christening scene was actually lifted from the animated film that Disney made years ago, with some of it being repurposed and additional dialogue inserted. The description of what happens afterwards also has this.
Sleeper Hit: The film was expected to be a Box Office Bomb for Disney and despite mixed reviews, it wound being a financial hit, grossing over 700 million worldwide.
In fact, it's domestically outgrossed films such as Godzilla, Amazing Spiderman 2, X-Men: Days of Future Past, 22 Jump Street, and Teenage Mutant Ninja Turtles. This is in part due to a weak summer box office.
The original script had King Stefan as a much darker character, being the half-fairy bastard son of the King rather than just a farmboy, who never actually loved Maleficent at all, and who murders his father to take the throne rather win it from the already-dying King as in the finished film.
It also included an actual Queen of the Fairies, Ulla, Maleficent's aunt, who cursed her with her horns to mark that she was a nuisance (her big wings were often disruptive), and Maleficent's father was also a minor character. Miranda Richardson and Peter Capaldi were cast as these characters, respectively. These scenes were filmed but they were sadly cut.
Various novelizations also feature a character named Robin, who would have been Maleficent's friend growing up. A small, winged faerie, he would have tried to warn Maleficent about humans, but in vain as she ended up befriending Stefan. He disappears from the narrative once Maleficent meets Diaval.
Maleficent was also supposed to be far colder to Aurora initially; instead of sending Diaval to care for her as a baby, she was to, effectively, leave her to die, and Diaval would end up secretly looking out for Aurora while bringing Maleficent around.
Diaval being the one to suggest Maleficent revoke the curse;
Stefan getting the idea to murder Maleficent from King Henry, who tells him that a true king needs to sacrifice even his loved ones to gain the crown;
and the pixies defecting from the Moors, rather than simply coming to the christening "to foster peace and goodwill."
Word of God: Screenwriter Linda Woolverton has stated that Phillip and Aurora will get together eventually.
She also said that the idea for the film's plot came about after she researched the original "Sleeping Beauty" fairy tale and saw that Maleficent was actually a fairy (most fans tend to mistake her for a simple witch). From there, she wondered why Maleficent didn't have wings like the other fairies, and came up with the story presented on screen. This is actually referenced in the film, during a conversation between Aurora and Maleficent.