What a great, refreshing character Dory is. And hilarious.
In the first book, she explains that she is the "little kid in the family," has an imaginary friend, Mary, and her older brother and sister don't want to play with her. They call her "rascal" (it isn't hard to imagine why, since she constantly gets in trouble and interrupts her siblings. Finally, her siblings create an imaginary "Mrs. Gobble Gracker" to frighten her. You'll have to find out the rest of the story by reading it yourself.