ANAHEIM, Calif. – “Blackfish,” the orcas-in-captivity documentary that has seared SeaWorld with negative publicity, prompted Pixar Animation Studios to rewrite part of its coming “Finding Nemo” sequel.

The script for “Finding Dory,” which is still in the early stages of production ahead of its planned 2015 release, initially had an ending that involved a marine park, according to a Pixar employee. But as a result of the sometimes harsh “Blackfish,” directed by Gabriela Cowperthwaite, and the resulting publicity battle SeaWorld has had to fight, Pixar decided to restructure that part of the story so that the fish and mammals taken to its aquatic center have the option to leave.

Walt Disney Studios, which includes Pixar, declined to comment.

Pixar movies change all the time while they are in the pipeline – that’s one of the benefits of animation. But in addition to reflecting the impact of “Blackfish,” the tweak offers a rare peek into the creative workings at Pixar, which keeps extremely quiet about its films until they are ready for release. The overall story line of “Finding Dory” is still a mystery, for instance.

John Lasseter, the Pixar co-founder, is scheduled to take the stage in Anaheim on Friday morning at D23 Expo, a sprawling Disney fan convention, for a presentation of the company’s more immediate animated projects, including “The Good Dinosaur,” which is set for release in the spring.