The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When Xavier is watching the shuttle launch, he has some sort of wheel on the right side of his hoverchair. Moments later when he regroups with Storm and Jubilee, the wheel is now missing. (00:09:17 - 00:10:07)
Chosen answer: The effect can be achieved in various ways. Split screen and image overlapping is one method. CGI can simulate body movements making it appear the characters are physically interacting, or a face can be superimposed over a body double. Lisa Kudrow's older sister, Helena, who looks almost exactly like her, was often used as her twin body double, mostly filmed from the back or the side and in scenes where one stood or walked in front of the other.
raywest ★