Uncle Cosworth is a Civil War veteran and resident of Ms. Macadoo's boarding house in 1947 Roswell, New Mexico in "Fellow Traveler".
After Roger crashes to Earth, he is discovered by Freddie Underwood and taken to Ms. Macadoo's boarding house for a hot meal, where he is pursued by Avery Bullock, Sr, Avery Bullock's father. Donning a hasty disguise as Ms. Macadoo's twin sister, Roger manages to fool Bullock, and delights the members of the boarding house. Going into town for a chile festival, Roger discovers that his ship's power source is being passed off as a piece of Heaven's wall at a tent revival. He successfully recovers the power source, but he is captured by Bullock. On their way to Area 51, he is saved when the group intervenes, although Bullock decides to take them all. They are saved when Clifton knocks him out.