Trivia: The real people of P3X-989 are called "Altarians."
SG-1 shows up, explores the compound, and is stunned. Harlan says he kept them unconscious so they wouldn't know of him or realize anything was amiss when he sent them back through the Gate. However, later the human SG-1 is woken up by their robot counterparts and the real Jack immediately says, "Harlan, where have you been?" But the "real" SG-1 never met Harlan, so how does Jack know his name?
At the end when Jack is talking to the robot Jack and motions to him to get his face checked out, you can see Teal'c go out of character and almost bust out laughing for a second.
At the beginning when SG-1 finds the computer terminal you see two of the exact same surge protectors that you see all over the SGC computer systems.
When there is a coolant leak, and Harlan is trying to glue or attach something to a pipe, he asks Daniel to hold something in place while he bangs it into place. I guess he needed more glue, though, because when Daniel let go, it moved.
There seems to be some confusion whether Altair is P3X-989 or PX3-989. (Jack says P3X-989 when they arrive, but all other times in the episode it's referred to as PX3-989).
When the two Sams are discussing the possibility of "recreating the neural structure," Sam 2 says it "...defies the Uncertainty Principle." Heisenberg's Uncertainty Principle deals with indeterminism and quantum mechanics, and (very simply put) the concept that mapping a phenomena alters the phenomena making it impossible to accurately measure the original phenomena. This all has nothing to do with mapping and copying neural structures.
Jack 2: And don't even think about trying to send a bomb to make sure.
Jack: I wasn't!
Jack 2: Yes you were - I know you!
Jack 2: Harlan, people are not supposed to live forever.
Harlan: Maybe not. But if you try a few hundred years perhaps you might change your mind. Yes?
Jack: You have my word, Colonel.
Jack 2: Call me Jack.
Teal'c: Was not a copy made of me?
Harlan: Oh yes, yes...but I had to disintegrate you.
Teal'c: I see.
Sam 2: We are identical, right down to the mole on our...
Sam: Hey! Shut up!
Jack: Harlan, where have you been?
Harlan: Extremely busy.
Jack: I can see that. Doing what?
Harlan: Oh, ah, creating your synthetic others. Saving the planet. Busy, busy.
Harlan: All will be well, you will see. And your friend too.
Sam: What? Teal'c?
Daniel: You killed him!
Harlan: He was malfunctioning.
Daniel: How will all be well with him if he is dead?
Harlan: You still do not appreciate the gift? Immortality, 11,000 going on infinity. I always say.
Harlan: No, no, you must stay, you are friends. New friends.
Jack: Friends? I don't even like you. Chances are I will never like you.
Sam: Probably thought we'd damage him...
Jack: Perceptive little runt.
Harlan: Hubald, he was the creator of all this, but he died very early...too early...Many secrets with him, so long ago.
Jack: How long, exactly?
Harlan: Uh, exactly? 99,207,000 of your...hours.
Jack: (immediately) Well, that's 11,000 years.
Carter: How did you know that?
Jack: That's right?
Carter: (calculating) Yeah.
Daniel: Wait, how did you know that?!?
Harlan: Ah...Cumtraya! Cumtraya!
Daniel: I think that's a greeting.
Harlan: Yes, it is.
Daniel: Oh, well, then...Cumtraya! We are explorers from a place called Earth. I am Daniel. Hello. (tries to shake hands)
Harlan: Oh, this is your custom, yes? Hello. You are the leader?
Daniel: Oh, no. That will be...
Jack: Me! Colonel Jack O'Neill. Kum-bi-yah.
Jack: Ladies and gentlemen, this is your Colonel speaking. Welcome to P3X-niner-eight-niner (sic) where it's a balmy...room temperature.
General Hammond's granddaughters, Tessa and Kayla, are named after Brad Wright's daughters.
Harlan and the robot duplicates of SG-1 return in the fourth season episode "Double Jeopardy"
Syndication air date: February 22, 1999.
The name of the character is almost certainly a homage to s.f. writer Harlan Ellison. Mr. Ellison is...a little less easygoing then Harlan here, however.
The Tin Man in The Wizard of Oz wishes for a heart, thinking that it would make him more human and therefore a better being. Harlan's mindset is a twist on that, thinking that mechanical is superior to human.