What episode features tribbles multiplying aboard Deep Space Station K-7?

The episode featuring tribbles multiplying aboard Deep Space Station K-7 is “The Trouble with Tribbles.”

The Enterprise is summoned to K-7 to protect a shipment of quadrotriticale grain. Trader Cyrano Jones brings small, furry creatures called tribbles to the station, and Lieutenant Uhura takes one aboard the Enterprise.

The tribbles reproduce at extraordinary speed, spreading through the station and starship. Their presence becomes dangerous when they consume the grain shipment, many of them dying after the grain is poisoned by the Klingon agent Arne Darvin. The episode combines a comic infestation plot with a Federation-Klingon confrontation.

Written by David Gerrold and directed by Joseph Pevney, the episode first aired on December 29, 1967. It was nominated for the 1968 Hugo Award for Best Dramatic Presentation but lost to “The City on the Edge of Forever.” Its later legacy includes the Deep Space Nine crossover “Trials and Tribble-ations,” which digitally places DS9 characters inside the original story. The station is K-7, not Deep Space Nine, which belongs to a later Star Trek series.