5. The Little Mermaid (Little Shop Of Horrors)
This is a rare feat of blatant cinematic plagiarism that's actually been fully admitted by its perpetrators, because they inadvertently lifted from their own prior work.
1986's classic horror-comedy musical Little Shop of Horrors is not a Disney movie, but the songs were composed and written by the legendary team of Alan Menken and Howard Ashman, who later worked on a number of iconic Renaissance-Era Disney movies.
Menken and Ashman's "Part of Your World" is widely accepted to be the most iconic and memorable song from 1989's The Little Mermaid, but while the pair were conceiving the song, they realised it bore a considerable similarity to Little Shop of Horrors' own cracker "Something That's Green."
In addition to both being quintessential "I want" songs in which the protagonist yearns for something greater, the structures, melodies and general themes are practically identical.
Granted it's not some deep, dark secret and there are far worse things than to self-plagiarise, which at worst could be deemed a bit lazy. They're both terrific songs regardless, and despite its inherent unoriginality, Part of Your World remains a smash-hit show-stopper from Disney's back catalogue.