The Kreetassans are among one of the first species encountered by the Enterprise NX-01 crew. The species is quite preoccupied with proper etiquette, rituals, apologies, and complex codes of social behaviour, and have a knack for learning the complexities of such social codes. Archer and his crew managed to offend the Kreetassans often. For example, the Kreetassans find eating in public a great taboo. Also, they learned not to bring a dog near the Kreetassans’ sacred trees….
The Kreetassans also have a highly complex language, but because of that fact, their brains are capable of learning ‘simpler’ languages quickly. They are also expert at manufacturing plasma injectors.
The Kreetassans likely joined the Federation at some point, so you can likely introduce them as members of the Federation. They may be fun to play and for you to invent new cultural details for, given that they could appear quite alien and be vigilant about etiquette and behaviour.