Karl Theodor Zelger was one of the main illustrators for Der Papagei, Der Schmetterling and Der Kiebitz, the children's magazines of the Verlag Steinsberg in Vienna in the 1920s and 1930s. Signing with a simple "Z", Zelger drew for the magazines between 1926 and at least 1938. From 1928 to 1936 he drew the continuing adventure comic series 'Peter und Willys Abenteur', remarkable for its fantasy elements and its use of speech balloons.