Chris Runco was a Walt Disney imagineer who worked on the original Star Tours ride at Disneyland. Runco designed Captain Rex, the pilot droid and main character of the attraction. Based on Runco's foam sculpt for the character, fellow imagineers Larry Sheldon and Lance Updyke created Rex animatronic puppets from aluminum.[1]
Sources
"Star Tours: Taking Off on a Star Tour" — Star Wars Insider 104
Bantha Tracks #35 on Hyperspace (content obsolete and backup link not available)
SWCA 2022: 5 Creative Lessons Behind the Making of Star Tours on StarWars.com (backup link)
Meet “Gil” – The Custom-Built RX Droid Delighting Fans at Star Wars Celebration Japan on StarWars.com (backup link)