Grandpa's back in this book, this time with a mashup of fairy tales, including Snow White, Little Red Riding Hood, Goldilocks, and Hansel and Gretel. He uses the tale to teach Russell, Elisa, Nora, and Teddy that kids of all ages who are neighbors can be friends, even if "some are older and some are younger."
Russell attends full day kindergarten. There is no mention of the fact that he is the only one in the series so far who goes to school for more than half a day.
By the middle part of this book Elisa is two years old. A bit later than that, Russell turns six, and it is mentioned that Teddy is also six. It's starting to bug me how this book leaps forward in time in such large increments.
I've noticed a few references to playing with Legos in a few different books throughout the series. I think it's the only brand name mentioned in the entire series. Maybe because there isn't any other way to describe Legos without calling them by name.
This is the first book in the series that refers to any sort of diversity whatsoever. At Russell's birthday party, a boy named Daniel mentions that his father speaks Hebrew, and Nora points out that Mrs. Rodriguez, a neighbor on the second floor, speaks Spanish. I would have thought that a series taking place in New York City would have more different types of people walking around in it.