Dr. Klotz was an individual in a detective novel Data was reading in early 2364 to become more prepared for a Dixon Hill adventure. In this novel, he proposed the investigative machine, a machine which would investigate crimes. (TNG: "The Big Goodbye")
This character was only mentioned in writing.
This character was mentioned in the instruciton manual for the 1983 video game The Witness
. Pages from this manual appeared in the graphics for the episode.