The brilliant and abrasive holographic engineer who created the Emergency Medical Hologram and modelled its face and voice on his own.
Lewis Zimmerman was a Starfleet holographic engineer based at the Jupiter Station research facility, where he developed the Emergency Medical Hologram programme. He used his own appearance and personality as the template, which is why the Doctor aboard USS Voyager looked exactly like him and shared his acerbic manner.
Zimmerman was proud of his work but disappointed when the Mark I version was criticised for its poor bedside manner and replaced. He later worked on a long-term medical hologram project for which he wished to use Julian Bashir as a model. Reginald Barclay was among his few friends, and holographic versions of Zimmerman occasionally appeared to the Doctor.
After Voyager made contact with Earth, the Doctor learned that Zimmerman was gravely ill and had himself transmitted home to treat him. The two clashed at first but eventually reconciled, and the Doctor helped cure him. Zimmerman's relationship with his creation explored what it means for a hologram to grow beyond its programming.