Beezus and Ramona first appeared, as supporting characters, in a series of books focused on Henry Huggins. Beverly Cleary later wrote Beezus and Ramona, which focused on Beezus and her family. However, her younger sister Ramona became so popular that the remaining books focused on Ramona. Beezus is still an important character, and Henry Huggins still appears but becomes a secondary character in the series he launched. The names are reversed in the title for this film because of the shift in focus to Ramona.
The name of the construction company that builds Quimby's new bedroom is Bendix, a reference to the name of the doll that Ramona bakes into Beezus' birthday cake in the book "Beezus and Ramona."
Although the title stems from the first of Beverly Cleary's Ramona books, the plot is lifted from the second and third.
Klickitat St. is a real street in northeast Portland, OR, where author Beverly Cleary grew up. When we see Ramona waiting for the bus and the number 73 rolls up, that would have been near the corner of Klickitat St. and 33rd Ave. Beezus is seen going to Grant High School, which is a real high school located about 1/2 mile south of Klickitat St. and 33rd Ave.
In the television show and the book, Beezus explains that her name is Beatrice. When Ramona started talking as an infant, she couldn't say "Beatrice". She said "Beezus" instead.