Lieutenant M'Ress served as relief communications officer aboard the U.S.S. Enterprise in 2270-2271. A Caitian, she very much resembled an anthropomorphic Terran lion. M'Ress had brown fur and a long brown mane, with amber eyes and a gentle, purring voice.
M'Ress appeared only in the Star Trek animated series, and then only in a few episodes. She was voiced by Majel Barrett.
A fair amount of fan fiction has been written about M'Ress, likely because she provides an easy way to mix the genres of 'furry' and Star Trek fiction. Also, because she's only appeared in a few episodes, the character offers a lot of possibilities to writers to develop her personality and history. M'Ress is also interesting as an example of a character that would be impossible to portray properly in live-action; writers probably enjoy exploring the abilities and attributes of a felinoid species in a semi-canon Star Trek setting.
Although no documentation exists outside of fan fictions, it's generally agreed that M'Ress was one of the first Caitians in Starfleet, and that she had a long and successful career.