Post-production
For the shot in which Tooms slides through a chimney, the producers hired a contortionist who could squeeze through small spaces. They filmed the shot with the camera standing below the contortionist. The chimney, which was "more like a belt than a pipe", was made to look much narrower than it actually was. Using computer-generated imagery, they were able to produce and elongate shots of the contortionist's fingers. Producer R. W. Goodwin believed that the contortionist—known only as "Pepper"—would only have limited success in fitting down the chimney set and would work mostly as a photo double. However, he was able to fit entirely inside the chimney; the production crew only needed to add some sound effects "of bones snapping and cracking".
The scene in which Tooms enters Scully's home was initially filmed in Hutchison's absence. The crew shot his entrance later, using a larger blue screen set. These shots were digitally merged so that Tooms would appear to emerge from a much smaller hatch than was filmed. The effect was kept to a minimum; Hutchison's footage was not "squeezed" too much, as both Carter and visual effects supervisor Mat Beck have stated their belief that "less is more: just a hint of the supernatural is all that is required".
Read more about this topic: Squeeze (The X-Files), Production