A disturbing new alliance forces the Federation and Klingon empire to put their differences aside and stave off the new threat of a Dominion-Cardassian alliance.
Actor Allusion: A possible one: actor Alexander Siddig, who plays Dr. Bashir (and his changeling doppelganger), is the real-life nephew of actor Malcolm Mcdowell, who had played the villain Tolian Soren in the 1994 movie Star Trek: Generations. Here, the changeling Bashir tries to blow up a star using a Trilithium explosive, just like Soren did in the movie.
Because I'm Jonesy: When the station receives a message from the Gamma Quadrant sent by Dr. Bashir, and then the crew learns that the Bashir on their station is no longer aboard, Sisko realizes that their Bashir is almost certainly a changeling.
Worf Had the Flu: By the time Worf fights the First of the Jem'Hadar on the station, Worf has already experienced progressive injuries from his previous 7+ opponents, which Bashir can only do so much about under the circumstances.
Worthy Opponent: Worf kicks several different kinds of ass during his forced fights on the prison asteroid. His sheer determination earns him the respect of the Jem'Hadar in charge.
Ikat'ika: I yield. I cannot defeat this Klingon. All I can do is kill him. And that no longer holds my interest.
You Have Failed Me: The Vorta Deyos has Ikat'ika killed for yielding to an opponent he was winning the fight against. He also tries to have Worf killed at the same time, but Worf gets beamed out at that moment.