While Robert Picardo primarily contributed to Star Trek: Voyager's story as the ship's Emergency Medical Hologram, he actually played an impressive array of other characters. Only ever really known as the Doctor, Picardo's role among the Star Trek: Voyager cast grew as the show progressed. The Doctor's time in the Delta Quadrant allowed him to become a sentient artificial lifeform and is still one of the most prominent Star Trek characters to do so within this category. With Picardo's upcoming appearance among the Star Trek: Starfleet Academy cast, it's obvious the Doctor is still a fan favorite.
It's not uncommon for Star Trek actors to play more than one character within the franchise, even if their multiple in-universe personas are never given a canonical connection. Picardo's various Voyager roles are different in this respect, as they all come back to the Doctor in one way or another. Regardless, the actor still had to find new ways to make each role distinct, or at the very least, worthy of existence within the larger story. Thankfully, Picardo always delivered on these niche assignments, even if a character he was tasked with bringing to life was only around briefly.
Robert Picardo Played More Star Trek Characters Than Voyager's Doctor
Other versions of the EMH MK I weren't Picardo's only secondary roles
Star Trek: Voyager fans will understandably recognize Picardo as the ship's holographic Chief Medical Officer, but the Doctor is just the tip of Picardo's Voyager character iceberg. For instance, he also played Dr. Lewis Zimmerman, the creator of the EMH and the person the Doctor has to thank for his physical appearance and initial personality traits. However, Zimmerman is Picardo's only flesh-and-blood Star Trek character, as all his other Voyager roles are artificial lifeforms, like the Doctor.
Other examples include the USS Equinox's EMH, whose ethical subroutines had been removed, as well as the falsely-remembered version of Voyager's Doctor as shown in "Living Witness."
Other examples include the USS Equinox's EMH, whose ethical subroutines had been removed, as well as the falsely-remembered version of Voyager's Doctor as shown in "Living Witness." That iteration of the Doctor was the result of the history books wrongly recording Picardo's character as an android rather than a hologram. Plus, he was a very unsavory version of Voyager's EMH. "Living Witness" also featured a version of the Doctor salvaged long into the future from Voyager's EMH backup module.
Picardo also played Dr. Zimmerman in Star Trek: Deep Space Nine season 5, episode 16, "Dr. Bashir, I Presume?"
Robert Picardo played another spin on Voyager's EMH when Lt. Tom Paris (Robert Duncan McNeill) altered the Doctor's Photons Be Free holo-novel to include a very unethical version of the ship's Chief Medical Officer in season 7's "Author, Author". Star Trek: Voyager also eventually reveals that the Doctor is the only remaining EMH MK I in service as a physician, as all the others were deemed unfit for purpose and reprogrammed for manual labor. Some of these repurposed EMHs are also shown at the end of "Author, Author."
Why Robert Picardo Played Multiple Star Trek Characters
The Doctor's holographic nature makes him an easy character to explore in other contexts
Because the Doctor is a hologram, he doesn't visibly age like his humanoid crewmates do. In fact, he looks pretty consistent throughout the Star Trek timeline, as proven by his unchanged physical appearance in Star Trek: Prodigy. Because of this, it's easy to slot Picardo into new roles that spin off from the Doctor with very little need to make him look different, because it often wouldn't make sense if he did.
Furthermore, he isn't the only one of his kind. Although he's the only EMH MK I to ascend to true sentience - even if unintentionally - there are countless others out there who all look identical to him. This accounts for his roles as the Equinox's EMH, the repurposed EMHs in "Author, Author," and even the Enterprise's EMH in 1996's Star Trek: First Contact. The biggest physical changes for Picardo are when he played Zimmerman, and the android Doctor from "Living Witness," but Star Trek: Voyager was still careful not to make either of them look unrecognizable.
