I used to sneer at those so tone-deaf as to mistake the soundtrack of Conan the Barbarian (1982) for Carl Orff’s arrangement of the Carmina Burana. (Which, by the way, ought to be pronounced cármina, not carmîna.)
This last Frinight I was at the Paramount theater in Oakland to see Monty Python and the Holy Grail in a slightly longer edit than usual; and before it there was shown a trailer for Conan with, guess what, the Orff. I gather it’s common for movie trailers to be made before the feature’s soundtrack is complete, requiring the trailer’s music to be borrowed from elsewhere.
On another occasion, someone in my presence mistook Orff’s “O Fortuna” for Prokofiev’s battle song in Aleksandr Nevskij.