Writer:	Brad Wright
Story:	Michael Greenburg, Jarrad Paul
Director:	Brad Turner
Star:	Richard Dean Anderson (Colonel/Brigadier General Jonathan J. "Jack" O'Neill (Seasons 1-8)),  Christopher Judge (Teal'c),  Don S. Davis (Major General George S. Hammond (Seasons 1-7)),  Amanda Tapping (Captain/Major/ Lt. Colonel Samantha Carter),  Michael Shanks (Dr. Daniel Jackson (Seasons 1-5, 7+))
Recurring Role:	Teryl Rothery (Dr. Janet Fraiser),  Dan Shea (Sgt. Siler),  Daniel Bacon (Technician),  Tracy Westerholm (Surveillance SF)
Guest Star:	Jan Rubeš (Nick Ballard),  Russell Roberts (Psychiatrist),  Jacquie Janzen (Nurse),  Christopher Judge (Quetlzelcoatl (Voice)),  Jason Schombing (Dr. Robert Rothman)

Syndication airdate: April 23, 2001. (edit)

(Jack and Sam call it a night, as ghost-Daniel looks on)
Daniel: What? That's it! What ever happened to working through the night? I do it for you. (edit) Sam: Do you get the feeling that Daniel's still around?
Jack: Kinda.
Sam: I guess it's cause we miss him.
Jack: Or radiation sickness. (edit) Nick: Now we must wait for the giant aliens.
Jack: That just has a nice ring to it. (edit) Rothman: Teleportation device...? I... what do you think?
Siler: I think you're gonna get fired. (edit) Jack: He's just a little anxious to see ol' Nick.
Nurse: Oh, are you close?
Daniel: No.
Teal'c: (overlapping) No.
Jack: (overlapping) Yes.
(Jack stares at Teal'c)
Teal'c: Yes, extremely. (edit)

When SG-1 entered the cavern with Nick, you can clearly tell that they are against a green screen, as when they start to cross the catwalk to the skull, the rocks above passed through Teal'c's head. (edit) Jack: Hey! If you’d been listening, you’d know that Nintendos pass through everything.
Jack mistakenly refers to neutrinos as "Nintendos". Nintendo (originally founded in 1889 Japan to produce hanafuda playing cards) is one of the largest and most powerful companies in the video game industry. (edit) Trivia: This episode marks the first appearance of Dr. Robert Rothman since "Forever In A Day." However, Daniel dreamed that story. So exactly when did SGC actually hire Rothman? (edit) When Daniel is out-of-phase, he can seemingly pass through solid objects. As is often the case in sci-fi shows, however, there's no explanation for how he can lean against the wall outside the elevator that Samantha gets into, sit on a cabinet in the control room, and stand on the floor throughout the entire episode. (edit) When Nicholas Ballard is "alone" in his quarters with invisible Daniel Jackson for the first time at the SGC and confesses that he can see and hear him, Dr. Jackson has a frustrated but excited outburst in which he touches a chair which is knocked slightly back. He should have passed right through it. (edit)

Quetlzelcoatl
Quetzalcoatl is the Aztec name for Feathered-Serpent, an ancient Mesoamerican god worshiped by the Aztecs, Toltec, and many Mexican and northern Central American civilizations. He is believed (by some) to be one of the four gods to have created the earth. (edit) The Skeptic's Dictionary: There isn't a shard of evidence that these crystal skulls are mysterious in any way. What is mysterious is their continued popularity and the continued mythology as to their origins and powers.
The Skeptic's Dictionary has a somewhat better researched and plausible story behind the crystal skulls, the conclusion is that most, if not all, were actually manufactured in Germany no earlier than 1850 or so, and any tales of ancient cultures is most likely a hoax. (edit)