Star Trek: Discovery saw an epic season end with the crew settling into the late 32nd century, but could a familiar face from Voyager make an appearance in season 4? With “The Burn” arc concluded, and the Discovery crew now free to set out on new adventures under the captaincy of Michael Burnham, an opportunity exists to include Star Trek: Voyager’s “EMH” The Doctor, and it is possible there might be two of him.
With the crew of Discovery now firmly integrated into the future Federation, they can finally build a new home together. During season 3, the crew struggled with the trauma of being out of time along with their grief for lost loved ones, and this must surely continue on into season 4, leading to the potential for Voyager’s Doctor to return–but perhaps not the version who made it back to the Alpha Quadrant with his crew.
The events of Star Trek: Voyager season 4 episode “Living Witness” recounts how a backup for the "EMH" activated into a museum on a planet in the Delta Quadrant around a hundred years ahead of Discovery’s arrival. The backup Doctor helped resolve a conflict between the planet's two warring races and once united, they gave him a vessel so he could travel back to the Alpha Quadrant. As “The Burn” is not considered a galaxy wide event, and assuming the time estimates are correct, it is entirely plausible that the backup Doctor did eventually make it home, perhaps decades ahead of Discovery. This homecoming could present a problem because it is probable the Doctor from Voyager also exists in this time. In the Star Trek: Voyager season 3 episode “Future’s End, Part II,” the Doctor’s physical limitations were resolved thanks to a 29th-century mobile (holographic) emitter, allowing him the scope to develop beyond his original program and exist outside the Sickbay. It is reasonable to conclude The Doctor might exist indefinitely, and by the 32nd century, Discovery’s crew observed holographic personnel having a large presence within the Federation, possibly a result of the Doctor’s own evolution. Should both versions of the Doctor meet, their curmudgeon personalities and unique experiences might create conflict, which has the potential for an interesting story that Star Trek: Discovery could explore.
Adding cast members from previous shows has great value, as seen in Seven of Nine’s appearance in Star Trek: Picard. Jeri Ryan’s inclusion was an enormous success, not just because Seven is a popular character but because her story enhanced the show and added more than just support to its titular lead. Further evidence for this can be seen by the appearance of the late Leonard Nimoy’s Spock, in the Star Trek: Discovery season 3 episode “Unification III,” where Spock’s appearance absolutely enhanced the story being told.
This makes sense, as the Star Trek: Discovery writers have been clear that adding guest appearances are not fan service, but for legitimate reasons of storytelling. If Discovery’s creative team does decide to include Robert Picardo as a cameo or guest, it certainly won’t be enough to simply turn on the Doctor’s program. So, with a legitimate story reason in place, the idea of bringing this beloved Voyager character back isn’t as farfetched as it might seem, and under the right circumstances could very easily work.