In an illusion experienced by The Doctor, Doctor Kaplan was said to be a neurologist posted to Jupiter Station during the late 24th century.

In 2371, The Doctor experienced a series of illusions, including one in which Reginald Barclay appeared, claiming The Doctor was really Lewis Zimmerman and the crew of USS Voyager were merely holograms. In Barclay's attempt to get The Doctor/Zimmerman to turn off the holoprogram, he claimed to have consulted with Dr. Kaplan, who said that if he couldn't get out of the holodeck within the next hour, that the radiation would completely oxidize The Doctor/Zimmerman's neuro-cellular structures. (VOY: "Projections")