I too have based a 3-shot jungle river-boat (-junk) adventure from the essence of Apocalypse Now. I enjoyed DM'ing that one a lot.I changed a Tomb of Annihilation subplot from the Fort Bellarian / Liara Porter explore mission. Now became an assassination mission of insane colonel Kurtz in the heart of the jungle darkness. A la Apocalypse Now
I do the same. Whenever I steal more than just a base concept, I try to keep it something obscure. If the players figure it out too quickly, it often ruins the adventure.I prefer to steal from books (especially older ones), since it is less likely my players have read the book than seen the movie. If I include a movie reference it's usually as a joke.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.