The Catalyst Hero.
Prompted by a discussion over on WayoftheRodent about the Die Hard movies.
Is John McClane a 'catalyst hero'? Not altering significantly himself, but acting as a catalyst for change in others? Even his reconciliation with Holly Gennero in the first one is more her forced re-appraisal of him rather than any redemptive transformation his ordeal has engendered. They still get progressively further apart as Mcclane reverts to type, till they are eventually divorced in the 4th movie.
Generally, a catalyst hero is the strongest reason for a film with a strong protagonist to generate successful sequels. You wouldn't expect Dances With Wolves 2 to grace your screen any time soon, for example. Kevin Costner had his journey, was reborn anew and brought his gift of knowledge back to the mundane world he left us behind in. We all walked away, wincing, the wiser. Not a catalyst hero, then, our lieutenant Dunbar. Similarly, Tom Hanks in 'Big'. These central characters tend to undergo their great journey, have their life-affirming experience and find themselves (and, concomitantly, us) changed by it forever. What's left to tell?
Indeed, (thinking aloud) take any bad sequel that does NOT involve a catalyst hero and maybe the reason they failed (discounting technical ineptitude) are that they:-
a) failed to expand on the main character or their journey in an original enough way
b) didn't find anything new to say about the hero or at least cause them to effect change in others
Matrix: Reloaded and Revolutions are good examples. Let's chuck Grease 2 in for good measure. Neo ran the whole gamut in the first one with some quasi-buddhist belt-and-braces brilliance. What was left to tell? The protagonist is changed forever and if he is not now a catalyst hero and no-one else is changing, all you've got left are action sequences and a message that has become repetitive - or worse - woolly and didactic to a sophisticated audience (i.e. practically everyone). Should these flagship 'journey' films always get remade then, rather than added to?
A catalyst hero has no such problem. Let's take some others and see how their follow-on potential flourishes, given that they themselves remain who they are while bestowing the opportunity for change on those they bump up against.
Eddie Murphy's character in Beverley Hills Cop - displaced from his ordinary world (just like Neo and Lt. John Dunbar) except here the two sidekicks in his new environment (Rosewood and Taggart) change most significantly, with the correspondingly smaller ripples spreading out from Foley's madcap splash. Sequels, it seems, are practically a no-brainer for the catalyst hero, probably because we ourselves ultimately fear change and cling to consistency. We know Axel will always be Axel as we know Indy will always be Indy, but we're happy to find out who or what they might cause change in next.
The Terminator series adds a twist to the concept of the catalyst hero. Emerging as enemy to John Conor in the first instance, then friend in the second. You could argue that the Terminator does himself change, but in a way that's arguably counter-intuitive to his silicon nature and certainly not entirely satisfying to audiences. We quickly find a voice for our misgiving, even if we don't know why it doesn't sit right. Well, here's why. The cyborg assassin shouldn't be having the human feelings he is credited with at the end of T2. It is a bit of screenwriting wish-fulfilment to tarnish his catalyst hero crown and give his inorganic innards an ineffable whiff of Hollywood meddling. We're not daft enough not to notice, even if we can't exactly explain what it is we're not seeing.
Other catalyst heroes? Ferris Bueller, undertaking his own great, but ultimately superficial journey. It is Cameron who changes most. Similarly, Marty McFly, perhaps one of the most potent catalyst heroes in the respect that practically everyone he comes into contact changes, albeit under the wonky auspices of Chaos Theory, where time is as much enemy as friend, and no outcome can be truly foreseen.
Catalysts come in all shapes and sizes, but they are, it seems, almost always profitable in terms of the sequel.