12. Magically Disappearing Glasses
Keep an eye on these glasses because it's not the only time that they'll appear on this list. For their first slot though, McCoy's birthday present to Admiral Kirk definitely raise a few eyebrows in the latter half of the film.
The Wrath of Khan celebrates the ageing of the principal cast, whereas The Motion Picture went to lengths to hide the obvious time that had passed for them. Here, some of the hair is tinged with grey, some of the waistlines are a little expanded and, in Admiral Kirk's case, the eyesight just isn't what it used to be. Kirk is allergic to the standard treatment for failing vision, so McCoy gives him a pair of 'antique' spectacles instead.
Later in the film, as Kirk and the rest of the escape part from Regula 1 are sitting in the Genesis cave, David claims that they have no time to sit around. Kirk, wearing his new specs, checks his watch and assures him that they do have the time. Mere moments later, he looks up and the glasses are gone. While it's absolutely possible that he simply took them off, it's much more likely that there was a continuity gaff here.