Who is this Doctor you speak of?

The Doctor is just one of the many artifical intelligence medical programs that were programmed and developed by the engineer Dr. Zimmerman. Zimmerman is The Doctor's figurative father of sorts because of this. There are dozens of EMHs, once occupying ships but soon they became obsolete and were replaced with more advanced programs, they were set to work on mining expeditions by Starfleet. The only EMH to not have this fate is our Doctor, due to him being stranded in the Delta Quadrant on Voyager. The reason The Doctor is so unique compared to his fellow EMHs is that he was left to be activated for 7 years straight at a time, which was not what the EMH program was made to do. Being allowed to be left activated for so long caused him to develop his own personality, interests, passions, and opinions. He outgrew his programming and became his own living being, helping those around him realize that holograms are not just tools.

Somewhere down the line The Doctor would fight for the rights of his fellow holograms all throughout the series. Even his EMH counterparts back in the Alpha Quadrant, setting up a domino effect to cause them to seek equality with organics.

The Doctor, as a person, is very passionate. He's heavily opinionated and outspoken, and when he takes a liking to something he really shows it. Within the first year of being left on he gained a primary interest for opera, singing, and music in general. Training his vocal processors and studying the extent of Italian opera, especially. But soon he gained even more interests, like a passion for holo-imaging (the 24th century equivelant to photography) as well as a general passion for undiscovered life, as he himself was given life so unexpectedly.

The Doctor's personality is considered an acquired taste by many of his fellow shipmates, from the moment he was activated many considered him to be vain and self absorbed. This was in part due to his creator, Dr. Zimmerman, basing the original EMH on himself. While The Doctor still retained a lot of what he inherited from his creator, eventually he overcame his original cold, stand offish personality. A lot of this was thanks to the help of his closest and first friend, Kes. An Ocampan girl who took medical training under The Doctor during her time on Voyager. But his other shipmates also helped him come out of his shell. With a combination of his friends and researching human hobbies and interests, he became a person of his own.

Aside from his tendencies to be self flattering, The Doctor is very eccentric and expressive. He could also be described as theatrical, and very very dramatic. Theres not a thing on his mind he wouldnt make known! Hes very self assured and there would rarely be a moment where he experiences self doubt. He takes great pride in his medical abilities and his social skills! As far as hes aware, hes the bestest friend anybody could ever have. I'm inclined to agree.