Tex is a robot character. Although he did not appear in a Pixar feature or short film, he was created by John Lasseter for Lucasfilm's THX sound system, which partnered with and certified Pixar films from 1996 to 2006. He appeared in three THX trailers. The first was released in 1996. A second trailer released in 1997, followed by a third in 2006. While he does not have any comprehensible dialogue, his occasional grunts and muffles were provided by Lasseter.
Tex flying around the THX logo in the first trailer
Tex in front of the THX logo in the first trailer
Tex with a moo can in front of the THX logo in the second trailer