Worf says "make it so". An obvious nod to TNG where Captain Picard says it frequently.
Aron Eisenberg, a trained martial artist, did all of his own stunts for this episode.
This is the only episode in DS9's mirror universe arc where Cirroc Lofton (Jake Sisko) appears. This episode establishes that Jake was never born in the mirror universe.
The mirror universe version of Worf makes his first appearance in this episode. Michael Dorn was originally to appear as Worf in "Crossover", but he was unable to do so because he was shooting the the final season of Star Trek: The Next Generation at the time.
Carlos Carrasco returns as an unnamed Klingon officer aboard the Regent's ship. It is unclear if this officer is the mirror version of D'Ghor, Carrasco's character from The House of Quark (1994).