The Trouble with Tribbles is an episode of the original series of Star Trek, first broadcast on December 29, 1967. It was written by David Gerrold, directed by Joseph Pevney .

On stardate 4523.3 Captain James T. Kirk and his crew are called to Deep Space Station K7 by a priority one distress call . The station is near Sherman's Planet, a world in a sector of space disputed between the Federation and the Klingon Empire. The terms of the Organian Peace Treaty were that the Sherman's planet would revert to whichever side could manage it most efficiently.

Kirk is furious when he later realizes the distress call was unwarranted, and the Undersecretary in charge of agriculture in the sector, Nilz Baris , just wants someone to guard the shipments of quadrotriticale grain bound for Sherman's Planet. A Klingon ship soon arrives at the space station and requests that its crew be granted shore leave. Kirk tells the Klingon leader Koloth that he can only bring members of his crew down 12 at a time, and that he will provide one security guard for each Klingon which beams down.

Meanwhile, amidst a few fist fights that break out between Klingons and Enterprise crew members, an independent trader, Cyrano Jones , sneaks some little furry animals called Tribbles onto the station, and starting with a purchase to Uhura, they quickly find their way onto the Enterprise as adorable pets. The animals chirp a relaxing trill that the crew find soothing. Klingons however, find tribbles very annoying. Tribbles emit an ear-piercing shriek of aggression whenever they are around Klingons, so the feeling is mutual.

The "trouble" with the tribbles is that they reproduce far too quickly; in the words of Dr McCoy, "they are born pregnant" and soon threaten to clog up essential ship systems and consume the supplies. Kirk realizes that if the tribbles are getting into the Enterprise's stores then they are a direct threat to the grain stores aboard the station. But its already too late, the tribbles have indeed eaten the grain. It appears the mission has ended in a fiasco.

However, in consuming the stores on the station there begins a massive die off of tribbles that alerts the Federation that the grain was poisoned. Furthermore, the tribbles also give away the identity of a Klingon agent who did the poisoning. The saboteur was the only human the tribbles didn't like. Upon a medical scan by Dr. McCoy, it was revealed the human was indeed a Klingon in disguise. Thus the tribbles redeem themselves and enable the Federation to score a diplomatic victory against the Klingons. As for Cyrano Jones, who introduced the species to the station, he is ordered to remove the tribbles from the station or be imprisoned for 20 years for transporting a dangerous lifeform off of its native planet; a clean-up task estimated to take 17.9 years.

Just before departing, all tribbles that were on the Enterprise are beamed onto the Klingon ship by Scotty, where, in his words, they will be "no tribble at all".