Jimmy was an individual in a detective novel Data was reading in early 2364 to become more prepared for a Dixon Hill adventure. In the novel, he was an elephant trainer. He was a former criminal who had gone straight for seven years and was now responsible for the care of the elephant Nellie. (TNG: "The Big Goodbye")

This character was only mentioned in writing.
The pages seen in the episode were actually from the detective novel, The Listening Man, by author John A. Moroso. This novel was published in 1924. Information on Jimmy was from pages 82-83.
Community content is available under CC-BY-NC unless otherwise noted.