... [Bob] Peterson seemed like the natural choice to direct Good Dinosaur — but he ended up getting removed in mid-2013, when the film was only about nine months away from its scheduled release date in early 2014. Producer John Walker also left the film at the time, to go work on Brad Bird’s live-action movie Tomorrowland. ...
After the film changed creative teams in mid-2013, “we changed the characters quite a bit,” said Ream. “They went from older to younger.” Arlo the dinosaur had been about 17 years old, but now he was 11. His siblings also became younger. ...
And so on and so forth.
None of the tales of rejiggering Dinosaur are out of the ordinary.
Ward Kimball told the same tale about Pinocchio, how everybody was stumbling around trying to find the through-line of the story and not having an easy time of it. (And even today, despite the glories of the characters, the multi-plane work, the art direction, some of the joints still show).
Sometimes troubles happen earlier in production, sometimes later. Gone With the Wind -- going on at the same time Pinocchio was in the process of becoming -- had shot principal photography for three weeks when the producer fired director George Cukor (who had worked on the flick for two-and-a-half years) and brought in director Victor Fleming.
Fleming pored over the screenplay and immediately told producer David Selznick: "David? Your f*cking script is no f*cking good."
(Fleming was less polite than John Lasseter.)
And they spent two frantic weeks rewriting the first half of the movie. And then started production again.
The point is that do-overs happen in film-making from time to time. Sometimes the end results are wildly successful, at other times not. When Thanksgiving arrives, we'll see what the changes made to The Good Dinosaur add up to.