Final answer:
The unusual aspect of the Robinsons' baby in 'Harriet The Spy' is not detailed in the provided passages, which cover other themes related to children and parenting.
Step-by-step explanation:
In Harriet The Spy, the unusual aspect about the baby of the Robinsons is not explicitly mentioned in the given extracts. In these various passages, the focus is on different scenarios such as bird watching, a mother's concern for her child, nursery control in a futuristic setting, and motherhood experiences in different contexts. Each of these vignettes provides insight into various characters' relationships with children and their thoughts on parenting, yet none directly describe the peculiarities of the Robinsons' baby from Harriet The Spy.