Tags from @pleasantartisanhottea
I *know* that in the original, Buttercup and Westley had this grand romance and Inigo took over the Dread Pirate Roberts name and Fezzik...did something. Did he have a plan? Maybe he becomes Inigo's first mate.
Humperdink and various soldiers catch up to Westley and the extremely useless Vizzini. Westley, recognizing the murderous fiance of his beloved, talks a good line and gets himself in Humperdink's...not good graces, the man is too suspicious for that, but at least begrudged tolerance.
Vizzini, of course, is executed before he can spill the beans. Or at least is gagged and taken to Rugen's secret torture dungeon. No big loss.
So that party heads back to the castle with the prince in A Mood (TM), and he's demanding someone bring him Rugen before he's even through the castle gates.
Meanwhile, back at Rugen's ACTUAL home (mini castle), Inigo is giving Buttercup a swordfighting lesson to pass the time and Fezzik is helping out with all those little chores that pile up while the lord is away. Like rearranging the furniture single handedly. The countess is actually quite charmed - he's very careful, and he keeps offering excellent suggestions about where to place different pieces for easiest use, and he doesn't mind moving things over and over when she changes her mind!
Anyway, the Nice Old King dies, poor man, and Humperdink summons all his nobles so he can rush through a coronation. Lady Rugen is all over the place, not knowing what to do, but she escorts Princess Buttercup and her sworn knights (aka they escort Lady Rugen) back to the capitol.
Something something, Inigo and Westley nearly come to blows over "that's my girl!" but then Humperdink opens his big dumb mouth and suddenly it's Westley and Inigo (and Fezzik) vs Humperdink and Rugen, and there's really only one way this can go.
Westley is now the king by right of conquest, assuming he even wants it, and Buttercup is putting her foot down that they are NOT breaking up their fun new gang, and Inigo and Fezzik are like "idc, man, whatever you want."
Anyway, Buttercup decides that SHE will be reigning queen, in her own name, and Prince Westley will be her consort and Inigo, newly ennobled as a count, will be her chief advisor. (And their lover, shhh.) Fezzik leads the Queen's Guard, and between him and Inigo, they whip everyone into actual effectiveness. Former-Countess Rugen becomes a lady-in-waiting to the Queen, which she likes much better than marriage to a man who plans wars and assassinations and new torture methods.
I'm not sure how Miracle Max fits in, but he definitely gets invited back to the castle. Maybe he revives the previous king ("he was only MOSTLY dead!" - Humperdink is terrible at poisoning), who then supports Buttercup's claim to the throne. He likes her, she's clever AND kind. The kingdom could use more of that.
Vizzini never recovers from his concussion and is eventually buried with the disgraced prince and count in an unmarked grave. Fezzik makes sure that lots and lots of buttercups are planted there every spring as a final "fuck you."
