The stiletto used by the Bounty Hunter is actually made of an aluminum/acrylic composite. No spring could be found that was powerful enough to fit inside the stiletto so a pneumatic pump was set up. A tube ran from Brian Thompson's hand to the stiletto for the needle to be pushed out of the cylinder. Also, the sound that the stiletto makes is actually made by the voice of Co-Producer Paul Rabwin.
Samantha: Is it too late for a game of stratego?
Mulder: It's 22 years too late.
Scully: Our friend from the CIA is about as unbelievable as his story. As is everything about this case. I mean, whatever happened to 'Trust no one'?
Mulder: Oh, I changed it to 'Trust everyone'. I didn't tell you?
Mulder was bringing a report for Skinner, but afterward, he walked out of Skinner's office with the report.
In the first sequence, Mulder has an oxygen mask on when he's in the tub. While Scully confers with the doctor, Mulder is seen in the background without the mask. It is back on in the next shot, though.
Mulder never returned home to tape a greeting on his answering machine, yet we hear a different one each time it is played.
Scully couldn't have called Mulder's cell phone since it was destroyed when he was hit by the car. He, however, could have called her cell phone after getting her answering machine.