Tribbles are the greatest enemy of the Klingons, as opposed to Starfleet. 1 / 7
Tribbles made their first appearance in the Star Trek: The Original Series episode The Trouble with Tribbles... 2 / 7
Which set up that the only things Tribbles do are eat and reproduce at a very fast rate. 3 / 7
They are also friendly to humans but quite antagonistic towards Klingons. 4 / 7
In Deep Space Nine, Worf revealed they had been declared enemies of the Klingon empire after Kirk had infested Koloth's ship with them. 5 / 7
Tribbles were later written into the prequel series Star Trek: Enterprise and Star Trek: Discovery. 6 / 7
Though the Klingons are known to be proud of their victories, they go out of their way not to talk about the Tribbles! 7 / 7