The cover of the novel is taken from a famous chalk drawing.

小说的封面选自一幅著名的粉笔画。

So Mary Poppins, Bert, and the two children are out in the park, and they decide to actually enter into, or jump into, one of Bert's chalk drawings.

所以欢乐满人间、伯特和两个孩子在公园里，他们决定真正进入或跳入伯特的一幅粉笔画。