Beginning in May 1991, Watterson took a nine-month sabbatical from Calvin and Hobbes, the first of two such leaves of absence during the strip's 10-year run. When he returned, he demanded that newspapers run his Sunday strips full size—one-half of a newspaper broadsheet—which allowed him to experiment with unusual panel sizes and shapes. (Typically, comic-strip artists must use the top panels of their Sunday strips for a throwaway gag, in case newspaper editors choose to save space by running only the lower two-thirds of the strip.) Inspired by George Herriman's full-page Krazy Kat strips from the 1920s and '30s, Watterson wanted to try something less rigid. Beginning in 1992, sometimes he would draw a single panel on Sundays. On other occasions, his Sunday strip would be filled with 20 small squares. In this strip, the third Sunday after Watterson's return in 1992, the "assembly line" snowballs are a clear metaphor for the comics, even as Watterson pokes mild fun at his own ambitions.