10 Biggest WTF Moments From Star Trek: The Next Generation

10. The Borg-Infested Universe

In the episode Parallels, Worf began uncontrollably jumping between alternate universes. Near the end, thousands of versions of the Enterprise-D began appearing in the same place, and Worf teamed up with an alternate Captain Riker to find his original crew.

They sent out a signal to all of the Enterprise's, explaining that they could stop the quantum anomaly by returning Worf to the ship matching his quantum signature. This was the only way to return all of the ship's to their proper universes, but when Worf set off towards his ship, he was attacked by one of the alternate Enterprises.

The attacking ship hailed Captain Riker, and another alternate version of himself appeared on the viewscreen and pleaded to not be sent back to his universe. He explained that the Borg had completely overwhelmed the Federation in his universe, and that the Enterprise-D was one of the few remaining Starfleet ships. The other Riker tried to reason with him, but he was determined to not return to the Borg-infested universe he came from. The ship continued to fire on Worf, and, attempting to disable their ship, the other alternate Enterprise accidentally destroyed them with a single photon torpedo.

This is undeniably one of the most horrifying alternate realities we've seen in Trek, even darker than the mirror universe. The terror in Captain Riker's voice when he pleaded that 'the Borg are everywhere!' will always send chills down the spine.

In the novel Q-Squared, it was explained that Worf refrained from telling those in his universe about this Borg-controlled reality because he found the implications of what happened to them to be far too uncomfortable.