Final answer:
Hillari Kimble, a character in Jerry Spinelli's novel 'Stargirl,' is known to be skeptical and occasionally hostile towards Stargirl but does not specifically create detailed theories about her background.
Step-by-step explanation:
The theories concocted by Hillari Kimble about Stargirl's background in the novel Stargirl by Jerry Spinelli primarily fell into a few imaginative categories. Hillari's theories are not detailed in the book, as she is more of a skeptic and a bully towards Stargirl rather than someone who spends time creating theories about her.
However, the students at Mica High School, where the novel is set, do speculate about Stargirl's unusual nature and background, pondering whether she might be an alien or have some other extraordinary origin due to her nonconformist behavior and unique personality.
The theories are more of a reflection of the students' own wonderment and the mystery that surrounds Stargirl than actual conjectures made by Hillari.