Dug this out of the crates for a thread just now, the crossfade between Mean Girls and Hackers via Halcyon + On + On.
https://exple.tive.org/blarg/2020/01/05/crossfade-dissonance/
It was the seed crystal of an idea I couldn't implement at the time, a Kevin Bacon Game for movie soundtracks: Can you get from one movie to another via seamless crossfade, and maybe turn the exercise into one (ridiculously long) movie?
Apparently there's now a soundtrack movie database, though, so maybe it's possible?