"I must preserve."
The SGC's computer mainframe is taken over by a sentient computer program from another planet. When the team tries to shut it down, it takes control of Carter instead.
"Entity" provides examples of the following tropes:
- Bottle Episode: Takes place entirely on the base.
- Brain Uploading: The entity uploads Carter's consciousness to the computer mainframe, allowing O'Neill to kill it while it's still inside her body.
- Brick Joke: O'Neill twice complains about "not getting his memos," in a callback to the previous episode.
- Contagious A.I.: A sentient program spreads throughout the base computer system before eventually jumping into Carter.
- Continuity Nod: The Planet of the Week is mentioned as being one of those from the Ancient database that O'Neill added to the dialing computers in "The Fifth Race".
- Death by Irony: The entity obviously identifies O'Neill as its main threat early on, and explicitly inhabits Carter to protect itself from him because "You will not terminate this one in order to destroy me." The entity obviously thinks it's being very clever as it explains this. However, it hasn't taken into account that inhabiting Carter's body is not the same as being Carter, and that it's suppressing Carter to death, meaning that she's being terminated anyway. This provokes O'Neill, who was overruled when the entity was apparently contained in the computer, threatening to wipe out the entity's home planet if it doesn't leave Carter, forcing it to kill itself to protect its people. If it had stayed in the computer, O'Neill would have continued to be overruled and it could have remained alive by trading on the information it offered anyway.
- Death of Personality: Fraiser speculates that the entity may have completely overwritten Carter's brain, effectively erasing everything that makes her her.
- Doctor's Orders: O'Neill is somewhat bemused when Fraiser starts giving orders left and right after the entity first comes through the gate, only to be told that she has superiority in cases of suspected medical emergency.O'Neill: Who put her in charge?
Hammond: The US Air Force. [Leaves]
Teal'c: In medical matters, Dr. Fraiser may overrule those of any rank. [Leaves]
O'Neill: ...I'm not getting all my memos. - Does This Make Me Look Fat?: O'Neill makes a joke to this effect when the entity starts playing security footage of the team in the briefing room.
- "Eureka!" Moment: Daniel has one when he realizes that Carter is now in the computer system, attempting to contact them.
- Genocide Dilemma: Subverted; O'Neill doesn't think twice about threatening to wipe out the entity's entire planet if it doesn't let Carter go. Though Hammond already had the address to the planet wiped from the dialing database. The entity has no way of knowing that, believing the threat to be very real.
- Industrial World: From what little we see of P9C-372 through the MALP's camera, it appears to be this - a landscape covered with buildings and machinery out to the horizon, under a dark sky with lightning in the clouds.
- Nice Job Breaking It, Hero: The heroes unwittingly damage the entity's homeworld with radio transmissions from the MALP, provoking it into retaliating.
- Not So Stoic: There are couple of instances where the cracks begin to show in Fraiser's professional calm as she's faced with the possibility of Carter's death.
- Shoot the Dog: O'Neill reluctantly zats Carter twice in order to prevent the entity from escaping. Thankfully, she is able to survive, as the entity has already transferred her consciousness to the computer mainframe.
- Sliding Scale of Idealism Versus Cynicism: Daniel insists that even if Carter is to die, it doesn't mean that she was wrong for trying to communicate with entity. O'Neill is not convinced. The episode itself leans toward the cynical side, as it is O'Neill's threats of force not Daniels negotiations that get results. O'Neill even essentially tells Daniel to shut up, because they are going to do things his way.Daniel: So basically what you're saying is… if we'd just listened to you in the first place and blown it up… No, seriously, I'm asking: is that what you're saying?
Teal'c: If we had destroyed the entity, Daniel Jackson, Major Carter would not have been adversely affected.
Daniel: Okay, look. I know your first instinct is to protect, both of you, that's your job, that's what you do but…no matter what happens, no matter how this turns out, Sam wasn't wrong to try to communicate with it. - Starfish Aliens: A sentient computer program that can also possess living humans.
- The Stoic: Jokingly lampshaded at the beginning of the episode as O'Neill and Daniel try to guess the expression on Teal'c's face, which remains as impassive as ever.O'Neill: You look tense.
Daniel: No, I'd say anxious.
Teal'c: I am neither tense nor anxious... Perhaps concerned. - What Measure Is a Non-Human?: Before it takes control of Carter, Daniel is adamant that they should try to communicate with the entity rather than simply blowing it up, as it's obviously intelligent. Carter agrees with him; O'Neill does not.Daniel: It's obviously fighting to survive.
O'Neill: So do bacteria!
[The entity brings up Carter's file on one of the monitors.]
Carter: It's trying to communicate.
O'Neill: So do bac—
