She was delighted and surprised. The 'new brother' was quite different in size, shape, and personality. "Look Out for Virgil" is a tale of introducing a new member to the family, and learning how to adjust to one another.
I (Debra, the illustrator for the two dog books) met Victor and Virgil, and worked from photographs to capture their "looks." Going into the minds of the dogs does require a little artistic licence, so the mice were invented to further state the dogs' reactions.
Isn't it nice to know there really was a Victor, and a Virgil? And yes - they did live with that many cats, too.