Mimi’s and Nina’s dog, Gusto, was named for Gustavus Adolphus the Great (Gustavus Adolphus Magnus) who was King of Sweden from 1611 through 1632. He (Gustavus Adolphus, not Gusto) founded Sweden as a major power during the 30 Years War and was known as The Lion of the North and Defender of the Faith for his defense of Protestant countries.
I never met Gusto, but I always felt like I knew him because of all the stories I heard growing up. My mental image is a friendly dog with lots of energy and curiosity who liked to roam the neighborhood and get into mischief.
One story that I recall was the time Gusto arrived carrying the lunch of a nearby workman. Catherine had to make a replacement sandwich and bring it to the workman.
Another time, Mimi describes walking home (possibly from school) in the winter when Gusto ran out onto the ice on a nearby pond. Mimi was mightily impressed when Nina when out on the ice to rescue Gusto.
I don’t have a photo of Gusto, but here is a photo of a statue honoring his namesake at Gustavus Adolphus College:
