Star Trek: 10 Times Canon Got In The Way
4. Not The Only Romulans
Couldn't let Voyager get away without some form of an entry on this list and it's only thanks to Picard's first season that it does.
Among the ex-Borgs aboard the Artifact were a number of Romulans who had been assimilated. Indeed these were the last crew to be integrated by the Cube and incredibly the only Romulans ever to have been taken into the Collective. Significant in many ways because amongst this group was Ramdha whose knowledge of the Admonition caused the collapse of the Borg sub-matrix and effectively neutered the Cube.
However, if we go all the way back to Voyager's third season and the pre-pre-Borg teaser episode, Unity it was clear that the Borg had actually assimilated a Romulan ship before as was proved by the presence of Orum in the Co-Operative community. Spin back even further and to The Neutral Zone from TNG's first season.
There it was suggested that the Borg were present around the Neutral Zone and were scooped up in a similar fashion to Jouret IV in The Best of Both Worlds. Ok, assimilation was only really introduced in that later two-parter but it still doesn't explain how Ramdha's ship was the only Romulan vessel assimilated when there were lots of other opportunities taken before.