Star Trek Picard: Every Easter Egg & Hidden Reference From 'The Impossible Box'

During his tour of the Artifact, Picard comments that he's never seen de-assimilation on this scale before. His previous experience (on screen anyway) is limited to his dealing with Hugh and the free Borg in "Decent, Parts I & II", and his introduction to Seven of Nine in "Absolute Candor" and "Stardust City Rag".

The USS Voyager, however, encountered numerous former Borg drones during its tour of the Delta Quadrant (home to the Borg) over the course of Star Trek: Voyager's seven seasons. The first time Voyager encountered freed Borg was in the third season episode "Unity" and a few episodes later the crew severed Seven of Nine from the Collective in "Scorpion, Part II".

Seven herself had previously been disconnected from the hive (along with three other drones) as told in flashback in the episode "Survival Instinct". The Voyager crew would go on to rescue assimilated children from a Borg cube in "Collective" and would assist numerous drones in escaping the hive in "Unimatrix Zero, Parts I & II".

As seen in both "Unity" and "Survival Instinct", not every doctor was as skilled as Voyager's doctor in removing Borg implants. This is reflected in "The Impossible Box" where we see drones with severe scarring which Hugh describes as rusults that are "far from ideal".