Remember Aardu, the wallaby that escaped from the Stone Zoo in 1990 and went exploring fot 11 days? The infamous Australian animal’s story lives on in Sheila S. Cunningham’s new book, “Willow’s Walkabout: A Children’s Guide to Boston.” Cunningham was at the Algonquin Club over the weekend to sign copies of the “Willow,” which she says was inspired by Aardu’s trek. The tale takes the reader on a journey through the Hub — from the Children’s Museum to the Freedom Trail and on a ride on some “wicked cool” swan boats. Years ago, Zoo New England caught the errant Aardu by setting traps filled with hay soaked in the urine of the female wallabies. We assume that Cunningham’s story has a more hygienic ending. The book was illustrated by Kathie Kelleher of Merrimac.