10 Star Trek Moments More Important Than You Realised

In the Voyager episode Demon, the crew encountered biomimetic lifeforms called "Silver Blood" on an uninhabitable Demon-class planet. These unique aliens have the ability to create copies of anything they make contact with. In the episode, Tom Paris and Harry Kim were duplicated, then later, in order to escape the planet, Janeway allowed them to recreate the whole crew, and left them to start a society on the Demon planet.

For a long time the fate of the duplicate crew was unknown, but, after 18 episodes, Course: Oblivion gave us the answers we were looking for.

Apparently the entire ship was duplicated and eventually the other crew forgot that they were copies and left the planet, setting course for Earth. Unfortunately, the Silver Blood is only able to survive on Demon-class planets, so, as time went on, the duplicate crew slowly began to die and revert back to their liquid state.

After finally realising their true identities, the duplicate crew tried desperately to find another Demon-class planet to settle, but, unable to find one in time, they all died and the ship was destroyed shortly before reaching the real Voyager, in an attempt to send them a time capsule of their lives.

Some fans even theorise that some of the episodes we've seen are actually from the perspective of the duplicate crew, though this has never been confirmed.