Ship of the Kreetassans, a species whose strict customs Enterprise offended twice, and whose departing vessel left an alien entity aboard in Vox Sola.
The Kreetassans were a species with demanding rules of etiquette. In Vox Sola, a visit by a Kreetassan delegation ended badly when they were shown into the mess hall, because they considered eating in public to be vulgar, and as their ship left, a translucent creature crossed over and began trapping Enterprise crewmen.
Travis Mayweather tracked down the Kreetassan vessel and apologised in exchange for information about the creature's homeworld. The Kreetassans were offended again in A Night in Sickbay, when Porthos relieved himself on one of their trees.