Jodie Foster was a longtime friend of the show's casting director, Randy Stone, and also a huge fan of the show. So when she was asked to provide a voice, she readily agreed. Foster nailed her line readings in one hour in a recording booth.
The sound of "Betty's" voice repeatedly pans between the left and right channels to heighten the sense that the sound is inside Ed's head.
Jodie Foster, who plays the voice of the tattoo, played Clarice Starling in The Silence of the Lambs (1991). Clarice Starling was one of the biggest inspirations for the creation of Scully's character. Gillian Anderson couldn't play Clarice Starling herself in Hannibal (2001) due to a special clause in her contract with The X Files that did not allow her to play another FBI agent. More than ten years later she played the disturbing character Dr. Bedelia Du Maurier in the series Hannibal (2013).
Gillian Anderson was really keen for Scully to have a sex scene and was very disappointed when it wasn't written into the script.
Actor Rodney Rowland was Gillian Anderson's date at the Emmy awards. She kissed David Duchovny first upon winning the Emmy, then Rowland.