Are toy story characters considered disney characters?

Quick Answer
Yes, characters from the Toy Story series are considered Disney characters because the franchise is a Disney–Pixar property.
Explanation
The Toy Story movies are produced by Pixar Animation Studios, which is wholly owned by The Walt Disney Company. As a result, all characters that appear in the Toy Story films—such as Woody, Buzz Lightyear, and Jessie—are part of Disney’s catalog of characters. Disney’s acquisition of Pixar in 2006 solidified this relationship, making every character created for Toy Story a Disney intellectual property. Consequently, merchandise, theme park attractions, and other media featuring Toy Story characters are distributed and marketed under the Disney brand. Therefore, from a legal and corporate standpoint, Toy Story characters are indeed Disney characters.