The upcoming Stargate Atlantis thriller "Doppelganger" will see an alien entity invade the team's minds -- using a familiar form. Executive producer Robert C. Cooper, who also wrote and directed the episode, described the story in an interview with GateWorld.

Beware of minor spoilers below.

"I've always been fascinated by nightmares and dreams," Cooper said. "So that's what this is about. It's about an alien entity that lives in crystal form. I've kind of paid a little homage to 'Cold Lazarus' and said, 'Well, OK -- there's something that we've established in the Stargate universe that we've never really dealt with before. And that is, again, lifeforms can exist in that state.'"

In the first season episode of Stargate SG-1, Jack O'Neill and SG-1 encountered a race of crystal-based beings who had been decimated by the Jaffa. When O'Neill touched one of the crystals he was knocked unconscious and duplicated by one of the beings -- who proceeded to return to Earth with SG-1 in an attempt to heal the colonel's 'pain.'"

"O'Neill went out, touched a crystal and all this stuff happened," Cooper said of the episode. "We've never done that again. And I thought, 'Well, wouldn't it be interesting if we found another crystalline life-form like that.' But in that case we were kind of lucky that it had reasonably good intentions. There was a sinister aspect to it in that we didn't know what was going on, but at the end of the day it was kind of just curious.

"So I took the flip side of that and said, 'What if it's a psychopath? What if it's truly evil?' And it enduces some pretty freaky nightmares."

The entity appears in the dreams of each member of Sheppard's team -- but as a familiar face. "What would our characters dream about? The fun part of the episode is, because it's Sheppard that initially engages and touches the crystal, and thus unleashes the entity on everyone, the physical form it takes in the nightmares is Sheppard. And so everyone is having these nightmares that are being pulled out of them by the entity, but Sheppard is appearing in those dreams as the sort of negative enciting force."

Cooper reached back not only to the first season of Stargate SG-1 in conceiving the story, but to his own childhood as well. "My dad took me to see Jaws when I was seven years old. I was seven. There's a line in the script: one of McKay's histories is that his dad read him 'Moby Dick' when he was seven years old. The line was: 'What was the man thinking?!'"

"I think I probably didn't sleep for two years," Cooper laughed. "Honestly, I probably needed therapy! This was not the sort of thing you did back then, but I probably should have gotten some sort of counseling. But instead I spent my nights thinking to myself, 'One day I shall control the power that left me so terrified!'"

The connections to the classic horror movie "Nightmare on Elm Street" were certainly not lost on the cast and crew. "The joke is in the show," Cooper said. "Sheppard at one point, when it's explained to him, says, 'So are we talking Freddy Krueger here?' And it's him. He also turns to Teyla at one point and says, 'Did I have a goatee?'"

"Doppelganger" will air in the first half of Atlantis's fourth season, which premieres this fall on SCI FI Channel in the United States! Learn more about upcoming episodes in GateWorld's Season Three and Season Four episode guides. Season Three is now airing Fridays at 9 p.m. Eastern/Pacific.

Thinking about it, according to Mallozzi's blog, Paul McGillion is scheduled to appear in three episodes in season 4 and, apparently, the mid season finale (with the title 'This Mortal Coil') is to be his doorway back. At the moment, we don't know where 'Doppleganger' will appear in season 4 but if we are to take Mallozzi's word for it, Beckett may not be the one appearing in this episode.

I hope it is Sheppard. I would love to see a darker side of him.

after seeing your photo I wouldn't mind seeing any side of you

While I may not disagree with you, that is not really very approrpriate, especially not for this thread. Next time, try using Personal Messages to hit on other board members.
Will the nightmares be laid out for all to see, or will they be in each person's head?

I hope that this ep isn´t gpoing to be "cheesy" if you know what I mean.But , I´m not worried at all.

I don't quite know what you mean...

You mean you hope it won't be a stupid waste of time?

No,I mean,exploring nightmares can become really good or become chessy if it is done in a "light" way.What I´m trying to say,id that I hope that the episode is "dark" and not to much comedy.

I like dark and deep.

I do hope for some character development... I like a certain richness and quality when exploring dreams in fiction. I like psychology though, so I like it when things make some sense.

I'm not really into the whole dream thing yes it was okay when it was daniel and omagh de sala
but even that one last year the real world,I watched it once and nearly fell asleep myself.
personally I prefer ones to do with the ancients. now that would make for a great spin off one that charts the ancients history from why they left (before they left)the orii galaxy to returning to earth 10,000
years ago. yes I do know that the characters couldn't be constant and you would have to skip a few centuries but it could be done,and well done at that.

Thank you for that wonderful trip into you mind... I am so pleased you felt obliged to tell us all of that... of course... Perhaps we should be pleased you decided not to create an entire new thread...

When did Daniel dream Oma? He died more than once... his mind was probed, he was on his deathbed... but dreams?