In Star Trek V: The Final Frontier Caithlin Dar (Cynthia Gouw) was the Romulan representative to Nimbus III, the so-called ‘Planet of Galactic Peace’. When she arrived on Nimbus III, she greeted her counterparts, the Klingon, General Korrd, and the Terran, St John Talbot, with optimism and a cheery disposition, although her positive attitude was not returned.
The diplomats were captured by the renegade Vulcan Sybok; under his mental manipulation they joined his ‘Galactic Army of Light’ and Caithlin Dar helped to create a hostage tape intended to lure a Federation starship into a trap.
Both Caithlin Dar’s name and appearance are un-Romulan. The movie novelisation explains that her name derives from her being one-quarter Human. This may also explain her lack of the typical pronounced Romulan brow. However, neither of these suppositions are ‘canon’. Memory Alpha suggests that the production may simply have tried to save money by completely covering what should have been Dar’s pointed ears.
Kenny Myers was the special makeup designer; Richard Snell Make-up Designs (Ben Gorman, Ron Pipes & Brian Wade) were responsible for the Klingon and Vulcan prosthetics.