What's left behind after the story has developed
The first episode of Poe's serial "Narrative of A. Gordon Pym" is standard "Here's a wild story about my sea voyage", but by the end Poe had written him into a corner where he really ought to die... so Poe stopped the series at a cliffhanger!
The serial "Varney the Vampyre", anonymous and probably by multiple authors, actually changed genres (horror, detective, romance, cynical outsider, misunderstood innocent, world traveler) over its 2 years and 237 chapters. One gets the impression nobody knew what to do with the character.
The pulp series "The Shadow" had three authors under the house name Maxwell Grant over 18 years and 325 books. The Shadow was the disguise of ex-war-hero and gangland crimebuster Kent Allard, until one author decided to write The Shadow as the disguise of millionaire playboy and scientific detective Lamont Cranston (contradicting without explanation earlier novels where The Shadow and Cranston appeared together). This change of identity and genre was reversed when the first author returned to the series.
There's some clear early-installment weirdness in the Pern books. The characters and world during the first part of the first book are pretty different (a lot harsher, for one thing) than even the rest of the initial trilogy. The first book was a fixup of two novellas, and McCaffrey had no plans for a 20-odd book series (or I believe any return to most of the characters) when she was writing that first novella.