The looks of many visual elements in Star Trek have changed over the years. One of the most prominent and famous changes is the design of the Klingon species. At first, Klingons were barely distinguishable from humans. This stayed the same throughout the first series but first changed in the original Star Trek movie when Klingons got their trademark forehead ridges. The look of the Klingons remained mostly the same from that point until the movie Into Darkness, which changed the look of Klingons but retained the basic design scheme. The next change came with Discovery, where the Klingon species went through a major redesign. That brings the current count of Klingon makeup designs to four.
These sudden changes in the appearance of a major species did not go unnoticed. A few episodes even tried to explain where these sudden forehead ridges came from. The question of visual continuity is a complex one. Each series of Star Trek has made changes and introduced its own visual style, but for the most part major elements of Star Trek remain relatively visually similar. Special effects and prosthetic makeup have improved since Star Trek first aired. Some people might argue that these innovation should be used, while others would prefer that the vision of Star Trek’s original creators be preserved.