I love it when movies have a narrative segment that is very highly stylised and sharply distinct from the prevailing style of the rest of the action. Examples of the sort of thing I mean:
The story about the Deathly Hallows in Harry Potter 7.1
The introduction to Watership Down
the introduction to Hellboy 2
the end Titles to Wall.E (albeit that there was no spoken narration here)
My Dream is Yours (Jack Carson/Doris Day) has a tell-me-a-bedtime-story with Bugs Bunny but I’ll be damned if I can recall if it’s totally animated or mixed live-action with Carson and Bugs.
At any rate is follows/advances action, unlike Gene Kelly dancing with Jerry the Mouse.
There was an episode of Duckman that did the reverse. There was an in-story movie based on Duckman’s life. It was a live-action sequence inserted into a cartoon show.
There’s been a few live action scenes in Family Guy too, one with Bobby Ewing, and another where Brian was a guest on Real Time with Bill Maher.
Instead of the usual “falling in love” montage, Xanadu has a sequence where the two main characters turn into animation and make animated googly eyes at each other. Before turning into fish. And then birds. And falling in love as animated fish and birds. And then back to people. It’s pretty awesome/awful.
And god, now I’ve got that song stuck in my head. Don’t walk awaaaaaaaaay…
In the episode Lysergic Acid Diethylamide, Fringe switched to a pseudo-rotoscope animated style for the bits that occurred ‘in the head’ of one of the protagonists.