Born and raised in Belgium, Morris moved to the United States in 1946 for six years. There, he worked for MAD magazine and met René Goscinny. After Goscinny's death, several other writers contributed to LuckyLuke, including BobdeGroot, the well-known writer of such very successful humorous series as Robin Dubois, Léonard and Clifton, the latter published in English by Cinebook.