Horsefeathers- a blatently paste and copied desciption from
http://www.tvacres.com/creatures_tribbles.htm
Tribbles - Furry little balls of fluff first featured on episode No. 42 "Trouble with Tribbles" on the sci-fi series STAR TREK/NBC/1966-69. Tribbles were soft cuddly pets about five-inches in diameter that cooed and purred a soothing sound that comforted the human ear. The reason the crew of the starship USS Enterprise had "trouble with Tribbles" was because these small creatures had a voracious appetite plus a reproduction/gestation period of 12 hours.
Taken on board the Enterprise when they stopped for some rest and relaxation at Deep Space Station K-7, the Tribbles infiltrated the ship's storage department that housed a special genetically engineered grain called Quadrotriticale (a four-lobed hybrid of wheat and rye) scheduled to be transported to Sherman's Planet to develop farming on that world.
With a seemingly unlimited supply of food, these furry little pastel-colored creatures multiplied at a geometrical rate. According to calculation's of the Vulcan science officer Mr. Spock (Leonard Nimoy) the Tribbles offspring's totaled 1, 771, 561.
The Tribbles gentle nature was only disrupted when a Klingon came near them. At that time they'd screech a warning noise. Many of the Tribbles were found dead when it was discovered the grain they had eaten had been poisoned by an enemy Klingon spy.
Cyrano Jones (Stanley Adams), the space trader who originally sold the Tribbles to Enterprise crew members, was later given the responsibility of cleaning up each and everyone of the Tribbles left at Deep Space Station K-7.
Scotty on Cleanup Duty
The Tribble creatures were created by writer David Gerrold and were later seen on episode "More Tribbles, More Troubles" on the animated STAR TREK series; on the motion picture Star Trek III: The Search for Spock (1984); and in the fall of 1996 Tribbles resurfaced on STAR TREK: DEEP SPACE NINE/SYN/1993-99 on the episode "Trials and Tribble-ations" when the Spacecraft Defiant traveled back in time to interact with the original storyline featured on "Trouble with Tribble."
Special effects man Jimmy Ruggs designed the creatures for the original live-action episode. To give them motion, he put small balloons inside some and moved them via air pressure from air hoses that ran offstage. Others had small wind up motors inside them taken from battery operated animals. .