Continuity mistake: When Arissa is first interviewed in Odo's office, she displays a 'data port' that is embedded below and behind her left ear in her upper neck. Her hair is styled to make it visible, and the port seems to be there for the entire scene, tho almost completely obscured at times. The second time she's in Odo's office, her hair style is the same, making it very obvious the port has now vanished, and it's gone the entire scene. For the third visit to Odo's office, the port appears and disappears at random. Apparently this scene was comprised of shots from the two separate shoots that made up the first two office scenes.
Plot hole: During the previous episode, we find out that Dr. Bashir has been replaced by a changeling. But for the changeling's ruse to work, he would need to carry out all Bashir's duties. Which means he'd need all his medical knowledge. Bashir graduated second in his class at Starfleet Medical Academy. To learn all that Bashir knew would have taken longer than the Dominion and Federation knew about each other. Not only that, but to pull off all this changeling pulled off, he'd need intimate knowledge of Starfleet, Bajoran and Cardassian technologies. There's no way a changeling could have learned all that knowledge in the time alotted. Even if you use the excuse of the Great Link, the Founders would still need the time to amass the knowledge and at least one of them to learn all the medical techniques Bashir would have known to transfer that knowledge to the others, otherwise it would have been a dead giveaway Bashir wasn't really Bashir.
Character mistake: In the scene in Sisko's office where he has contacted Rear Admiral Bennett, Bennett says "Two hundred years ago, we tried to improve the species through DNA resequencing, and what did we get for our trouble? The Eugenics Wars." This puts the wars in the 22nd century, and differs from every other mention of them, where they occurred in the late 20th century, not the 22nd century as Bennett implies.
Continuity mistake: On the old Enterprise bridge, Sisko is shown at a bridge station, and the person next to him, close to Dax's position, is wearing a gold shirt. When Kirk comes onto the bridge, the person next to Dax now has a red shirt, which was the original crewman's shirt in TOS.
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