Can we list some well-known films where Protagonist and MC are not the same? The famous example from the Dramatica instructions is Atticus and Scout in To Kill a Mockingbird. Here are some others, where, in my my mind, Protagonist and MC are split. (We can argue here on this forum too, I suppose!)
Protagonist: Lewis (Burt Reynolds)
MC: Ed (Jon Voigt)
IC: Also Lewis?
Why: Lewis is the go-getter. Trip wouldn’t have happened without him. Most of us are more like Ed–we might go along for the ride. Ed toughens up as a result of this trip.
Film: Ferris Beuller’s Day Off
Protagonist: Ferris (Matthew Broderick)
MC: Cameron (Allan Ruck)
Why: Again, Ferris is the go-getter, and most of us would like to be Ferris, but we are not. We are Cameron. Cameron most definitely changes bc of Ferris–deciding to stand up to his father.
Film: Mosquito Coast
Protagonist: Allie (Harrison Ford)
MC: Charlie (River Phoenix)
Why: (More on this later)