Disney movies are big business in Hollywood, precisely because audiences know exactly what they're getting. You want singing, dancing animals? You got 'em! You want year after year of continuously disappointing ‘Star Wars’ sequels? You got that too! Ever since Walt Disney first picked up a battered old copy of Cinderella, read the scene where the ugly stepsisters hack off parts of their own feet to fit them in the glass slipper, and said “you know what? This would make an awesome kids’ film,” Disney movies have been borrowing their plots from some seriously dark places.

The Fox and the Hound: puppy gassing and rabies

1981’s The Fox and the Hound is chiefly remembered for Tim Burton and for being a moral muddle. Come the end of the film, fox Tod and dog Copper may have proved they can still be friends in a society that doesn't want them to be, but they're also keeping their distance and not actually acting like friends at all. There's no such moral ambiguity in Daniel P. Mannix's original novel. As far as Mannix seems concerned, the only possible message is nature is horrible, everything dies, and the gassing death of baby animals is a totally legit topic for a children's book (via Tor).

Peter Pan is just the biggest jerk

In 1953, Disney introduced the filmgoing world to Peter Pan, the mischievous boy who whisks Wendy away to Neverland. By that point, the literary world had already known Peter for 50 years, starting with J.M. Barrie's 1904 play Peter and Wendy and its 1911 novel adaptation. They also knew he wasn't merely mischievous. The Peter penned by Barrie went beyond naughtiness and into a kind of transcendent space of jerkiness. Put simply, the original Peter Pan was a schmuck.

The biggest difference comes when Wendy and company decide to go home. In the film, they wake up in their beds to discover a single night has passed. In the book, it's been months and their parents are half-mad with grief.