- Star Trek: The Motion Picture
- Star Trek II: The Wrath of Khan
- Star Trek III: The Search for Spock
- Star Trek IV: The Voyage Home
- Star Trek V: The Final Frontier
- Star Trek VI: The Undiscovered Country
- Star Trek Generations
This Alpha Quadrant species has a very complex language — which made for a problematic first contact with Enterprise NX-01. The Kreetassans consider eating and mating to be similar activities, and were therefore deeply offended when they observed the Enterprise crew eating in public. The crew tracked them down again when a strange, symbiotic organism transferred itself from the Kreetassan ship to Enterprise, taking some crewmembers captive. Luckily, the Kreetassans had learned English, and were able to communicate effectively with Ensign Travis Mayweather.
After Mayweather delivered a proper apology for the crew's faux pas, the Kreetassans provided him with the coordinates for the mysterious organism's homeworld. Captain Archer managed to offend the Kreetassans yet again when he and his crew visited the Kreetassan homeworld to obtain a plasma injector. Apparently, Porthos urinated on one of the Alvera trees outside the Hall of Diplomacy — the Kreetassans consider these trees to be cultural treasures. Captain Archer later performed an elaborate ritual of apology, which involved using a chain-saw to cut off pieces from a recently-felled tree and arrange them in a certain pattern.