The book series was first introduced in the strip from July 26, 1970, in which Charlie Brown reads one of the books to Snoopy as a bedtime story. In the strip from April 9, 1971 Snoopy can be seen reading a part of one the books, which reads, "And so the six Bunny-Wunnies said good night, and went to sleep. Their adventure was over, and all ended well".