- One member of their species was referred to as a Berikazin in Alan Dean Foster's adaptation of TAS: "Time Trap" in Star Trek Log Four. In both the Orion Press and Star Trek: Liberty continuities, the Tzenkethi was another name for the Kzinti. Also, in the RIS Bouteina and Star Trek: The Stoneship Files continuities, Kzinti were the singular and adjectival forms, while Kzintis was the plural form.
- The Kzinti seen in nearly all Trek continuities except The Animated Series are distinguished by having tufted ears, rather than webbed ears, as they do in Known Space.
Kzinti telepaths were addicted to a drug extracted from the sthondat lymph, could do telepathy for eight hours before having to sleep for 20 hours upon taking a telepathy-inducing dose of said drug, could probe minds within a 2,500-kilometer radius, and telepathy was a painful ordeal for its target, unlike Malachorians. (Star Trek: The Stoneship Files: "Chronicles of Taladu")
- In Larry Niven's Known Space series, the gender dimorphism of the Kzinti -- in which the females were smaller and only borderline sapient -- was not an original feature of the species.
Also, they had no respect for espionage or banking, as they considered these two lines of career as being "honorless". They had a blind spot towards females of many races, disregarding their combat capabilities, often leading to their undoing. (RIS Bouteina: "Miracle in Whoville")
The Kzinti have had some capacity for space travel for some time. It was thought the Caitians of the planet Cait (15 Lyncis) are descended from an ancient Kzinti colony. (TAS novel: Star Trek Log Five) It was known that they were mortal enemies of the Lyran Star Empire and that they fought three wars against them, resulting in their defeat. (RIS Bouteina)
- It should be noted that these wars had a de facto end, but no formal treaty could be signed because of hand-to-hand fighting between diplomats until 2386, when the Lyrans decided to rely on Romulan and Hydran diplomats rather than their own to negotiate with the Kzintis.
Prior to first contact with Terrans, the Kzinti had met -- and fought against -- the Tellarites, the Andorians, the Vulcans and the Klingons. The four Earth-Kzin Wars were precipitated by a disastrous first contact, when the Seeker-class UES Andrei Sakharov was attacked by Kzinti police cruisers in 2048. (Federation Spaceflight Chronology, vol. 3)
Between the Earth-Kzin conflicts of the late 21st century and the mid-23rd century, there were numerous skirmishes between vessels of the two starfaring races. A group of secessionist Kzin, calling themselves the M'dok, engaged Federation Starfleet vessels in several incidents over a two-year period in the 2160s. (Federation Spaceflight Chronology, vol. 7) In 2226, the Federation colony on Slavin H-3 was defended from a Kzinti attack by the Kestrel-class cruisers USS Caudiptyrex (NCC-1411) and USS Goshawk (NCC-1423). (The Starfleet Museum: Museum Timeline)
The Federation and the Kzinti fought a brief war in the mid- to late-2250s, simultaneous with Federation forces battling the Klingon Empire. A peace treaty with the former, and at least a cease fire with the latter was achieved by 2257. (Absolute Horizon)
Kzinti pirates attacked the interstellar liner SS Vymastre of Vega in 2284. Three-fourths of the crew and passengers were killed (and many eaten) before Federation starships — including the USS Constitution — engaged the pirates in combat. (Star Trek: Shadowstar Station: "Vymastre")
During the ISC War of Pacification, the Kzinti destroyed an ISC shipyard in the Tovolo system, resulting in a partially artificial asteroid field, where the Wyldefire Compact was defeated by a joint Federation-Lyran force in 2416. (Star Trek: False Vacuum: "Scrap Yard Vegas")
Little is revealed about Kzinti economy other than the following things: their bankers were very aggressive investors, they exported weapon toys and their currency was the strakh. (RIS Bouteina: "Toy Dream")