The original script had Mulder break down in tears after learning of Samantha's fate. David Duchovny didn't want to play it that way and asked director Kim Manners to trust his instincts. Instead Duchovny played the scene with such relief and acceptance that he brought tears to the eyes of the cast and crew.
David Duchovny was evidently delighted and relieved when Frank Spotnitz told him that this was the last time he'd have to play Mulder agonizing over what became of his sister.
This is the 150th X-Files episode.
Mulder's mother's apartment is actually Scully's apartment redressed for the occasion.
The opening sequence involving children climbing out of graves was shot in Griffith Park in Los Angeles. Worried that the children would be emotionally affected by the fact that they were essentially playing dead kids, director Kim Manners had them believe that they were actually playing in forts.