Mimic device
From The Stargate Omnipedia
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Mimic device
Alien device used by the mimetic aliens. The device allows a complete physical duplication of any individual that has been processed.
KEY EPISODES
Foothold - Aliens overtake the S.G.C. and use mimic devices to masquerade as Stargate personnel.
Smoke and Mirrors - Twelve mimic devices are stolen from Area 51 and used to further the plans of the N.I.D.