9. Chell's Here Too - Learning Curve
When considering improvised moments in Star Trek, there are those that are decided upon behind the scenes as well. These may be script additions at the eleventh hour, or simply visual cues and clues to support the scene. One such moment appeared in the final episode of Star Trek: Voyager's first season, Learning Curve. Here, Tuvok is tasked with helping several of the former Maquis crew adapt to life onboard the starship.
There is a scene in which the camera is focused on three of the Maquis. Director David Livingston chose to focus on them, omitting Crewman Chell from the shot. Then, Chell would step into the foreground, with the audience never having known he was there. This was done to give the moment a slightly deceptive and menacing feel, with Chell suddenly dominating the shot.
It was an excellent, subtle addition that let Livingston throw the audience slightly off-balance without giving anything away in the episode. Chell would of course go on to be mentioned many more times throughout Voyager, including that time he wanted to replace Neelix in the mess hall.