“Menace” is episode nineteen of season five of Stargate SG-1.
SG-1 are on a planet formerly occupied by a, now destroyed, advanced civilisation when they come across the preserved body of a young woman. Even though she appears dead and preserved, she isn’t – she’s actually an artificial lifeform of some description, possibly an android, which they then take back to the SGC. Carter thinks she can recharge and reactivate the android. So she does.
The revived android doesn’t know what happened – and doesn’t even seem to know that’s she’s an android – but her civilisation was destroyed by the Replicators. The first planet in the Milky Way where evidence of the Replicators has been discovered. The Replicators are the threat that’s even greater than the Goa’uld that the Asgard are currently fighting in another galaxy. The Replicators are bad.
This is an episode I have definitely seen before.