Hansel and Gretel is an old German tale that comes to us via the Brothers Grimm. (Read the story in The Complete Fairy Tales of the Brothers Grimm [398.21 COM].) We have several picture book versions in our children's room, including the Caldecott Honor award winner illustrated by Paul O. Zelinsky [JP HAN].) I'm sure you remember the story, so I won't bother to summarize it, but, in reading the Grimm version in The Complete Fairy Tales, I found that a duck ferried Hansel and Gretel to safety after their escape from the witch. I don't remember a duck in any version I have seen previously. Of course, in adapting a tale for a picture book, one would tend to eliminate anything that is not essential to the story. But it leads me to speculate about the reasons for the duck to begin with.
I found out about the duck at this site, which contains an annotated version. I found the "Modern Interpretations" booklist of particular interest. (What did you expect from a librarian?)
Besides reading the story, you can listen to the opera version by Engelbert Humperdinck [CD OPERA HUM]. We recently purchased the CD with Sir Charles Mackerras conducting the Philharmonia Orchestra (London) because it was awarded a Grammy this year for "Best Opera Recording." If you want a real treat, the Boston Lyric Opera is performing Hansel and Gretel on Sunday, April 13, at John Hancock Hall. Click here for more information.