Six-legged, arboreal, carnivorous, empathic, possibly telepathic mammals native to the planet Sphinx, where they are a protected species. The colonists were first made aware of them when the 'cats instituted a raid of the gardens and stole all the celery. Every 'cat seems to have a weakness for celery and will forego their normal behavior to beg for it.
Some 'cats adopt humans; there is not much known about the actual process by which this happens of how the 'cats choose their partners. Suddenly an empathic link is formed between a human and a 'cat when their eyes meet, after that they are mentally connected for life. The process seems similar to "recognition" in The Dragonriders of Pern series by Anne McCaffrey and being "Chosen" by a Companion in the Valdemar books by Mercedes Lackey.
The Ninth Amendment to the Star Kingdom's Constitution granted treecats special status as the indigenous intelligent species of Sphinx. There are laws that protect their corporate claim to just over a third of Sphinx.
Main Treecat Character
Nimitz (m)
Adopted Honor Harrington when she was a child (very rare). Main character who has appeared in every HH novel. He is the proud owner of an original Paul Tankersly treecat skinsuit.
Other Treecat Characters
(through book VII 'In Enemy Hands')
OK, if you haven't read ALL 7 of the books you may not want to check out the other Characters, as there are spoilers contained within. (I hope to add info from the compilation soon.
Don't say I didn't warn you.