Star Trek: 10 Characters That Faked Their Way Into Starfleet
9. The Vindicator
One of those 'even replicated butter wouldn't melt' types, the outwardly innocent, and apparently Trill, Ensign Asencia of the USS Dauntless was hiding a secret greater than Casperia Prime. Asencia was, in fact, a member of the Vau N'Akat, a species who called the Delta Quadrant home. She had been sent back in time, along with scary robot pal, not (merely) to infiltrate Starfleet and the Federation, but to destroy it as revenge for first contact gone wrong. Asencia wasn't Asencia, she was The Vindicator, one of The Order!
As an audience, we met Asencia/The Vindicator in full-on Starfleet subterfuge, but we don't know anything about how she achieved it in the first place. It's perhaps most likely that the young Vau N'Akat, errm, let's say, 'replaced' an already existing Trill officer when she decided to hitch a slipstream ride with Admiral Janeway. Showing the murder of a bright-eyed ensign, probably not long out of the Academy, might have been juuuust a bit too dark, however, for a show aiming at a younger demographic (amongst others).
However the infiltration happened, Starfleet seemingly hadn't learnt anything from the blue gills. Why wasn't anyone checking the backs of necks?! With a touch of a nape's button, The Vindicator could switch to become Asencia and then back again. She stopped pressing it for good when she finally got aboard the Protostar to put the Vau N'Akat's Starfleet-ending plans into execution.