Screenplay: The Trouble with Tribbles

Overview
"The Trouble with Tribbles" is a 1967 screenplay by David Gerrold for Star Trek: The Original Series, season 2, that turns a simple comic conceit into a memorable episode of character comedy and escalating chaos. The story hinges on the introduction of the tribble, a small, furry, purring creature whose most notable trait is its prodigious rate of reproduction. What begins as an amusing novelty quickly becomes a Shipwide crisis as tribbles breed uncontrollably, infiltrate machinery and supplies, and force Captain Kirk and his crew to deal with both practical and diplomatic complications.
Gerrold's script balances slapstick with sharp plotting: the tribbles function as a running gag, a logistical nightmare, and ultimately an inadvertent detective tool. The episode keeps dialogue brisk and situations absurdly plausible within the Star Trek universe, letting the personalities of Kirk, Spock, McCoy, and the supporting cast carry both the humor and the stakes.

Plot Summary
A traveling trader named Cyrano Jones brings the first tribble aboard the USS Enterprise as a novelty, and the animal's gentle purring and appealing appearance lead crew members to adopt them. Their charm is undercut when it becomes clear that tribbles reproduce at an exponential rate. As tribble populations expand in quarters, corridors and engineering, the ship finds itself literally overflowing with fuzz.
The Enterprise is en route to space station K-7, where a dispute over grain shipments bound for Sherman's Planet has drawn a Klingon presence and heightened tensions. The tribbles, attracted to warmth and grain alike, infest storage areas and reveal unexpected clues. Their presence exposes a clandestine scheme aimed at sabotaging the grain, and the creatures' ubiquity helps tip the balance in a diplomatic confrontation with Klingon agents. The climax resolves the immediate diplomatic danger while leaving behind the comic image of crew and visitors alike buried under a tide of tribbles.

Themes and Tone
At its heart, the episode uses humor to deflate militaristic posturing and to examine how small things can produce large consequences. The tribbles are emblematic of unanticipated side effects, what starts as an emotional comfort becomes a logistical and political headache. The script amplifies contrasts between characters: Kirk's exasperated command, Spock's analytical detachment, McCoy's irritable humanity and love-hate banter with Spock. These interactions anchor the comedy and keep the situation grounded in recognizable interpersonal dynamics.
The episode also lightly satirizes bureaucracy and the absurdities of diplomatic brinkmanship, using the tribbles as a mirror for how quickly order can give way to disorder when systems are overwhelmed. The tone remains playful throughout, with physical comedy and witty exchanges compensating for the practical peril the creatures create.

Legacy
"The Trouble with Tribbles" quickly became one of the most beloved episodes of the original series, celebrated for its wit, memorable creature design, and tight storytelling. The tribbles themselves became an enduring piece of Star Trek lore, resurfacing in later series and spin-offs as a nostalgic and mischievous reference. Gerrold's screenplay is often cited as a standout example of how genre television can blend comedy, character work and plot mechanics into an episode that entertains while still contributing to the ongoing worldbuilding of the franchise.
Beyond fan affection, the episode's success demonstrated that Star Trek could shift tone without losing its essence, proving that a show built on space drama could also excel at lighthearted social satire and pure comic invention. The image of Captain Kirk wading through a sea of small, purring creatures remains one of the franchise's most iconic and frequently quoted moments.