First seen in the sixties series of Star Trek ("The Trouble With Tribbles") these friendly and attractive creatures are the rabbits of the sci-fi world...only more so!
Given the right food (Quadrotriticale - a type of grain) a handful can become several thousand within a few days or even hours.
Tribbles are inoffensive and friendly to all species except for Klingons (who regard Tribbles as vermin). The Klingon empire ruthlessly massacred all traces of the Tribble species until a few were saved by the members of Deep Space Nine who after a trip into the past (DS9 "Trials and Tribble-ations) took them back to the future.
A Tribble is very useful for spotting Klingons in disguise as when in close proximity to a Klingon they become agitated and their customary cooing and chirping (very relaxing for humans) becomes a harsh trilling.
Click the Tribble