The CEO of Pixar awsers the question about Buzz Lightning

Peter Docter, director of Pixar, has finally answered the Toy Story inquiry about the famous ranger of intergalactic space, Buzz Lightning.
While the release of Soul has been a great success and received more than positive reviews since its Christmas Day release, fans are still wondering about a mystery that has been hanging over the Pixar Universe for a few years now.
In the first part of Toy Story, Buzz says that he doesn't believe he is a toy at all, but behaves like one when he is in front of humans. According to Docter, this facet of the film was discussed first part of the production in 1995. In the end, the team decided that this part did not matter, that the storytelling process mattered more. It focused more one the aspects of the plot that the public will be the most interested in.
No deeper explanation than that to the warden.