 In tradition with the show's animation style, they are both composed of simple geometrical shapes, and are animated with use of a computer, though they are given the impression of being construction paper cutout compositions animated through the use of stop motion, which was the technique used to animate the "Spirit of Christmas" shorts and the show's first episode.Gerald is voiced by series co-creator Matt Stone and Sheila was originally voiced by Mary Kay Bergman and is currently voiced by Mona Marshall.Their first names are derived from the first names of Stone's parents, Gerald and Sheila Stone.