...that every time the mirror universe has been visited on Deep Space Nine, a Ferengi has been executed? In "Crossover", Kira Nerys killed Quark; in "Through the Looking Glass", Elim Garak killed Rom; in "Shattered Mirror", Kira killed Nog; in "The Emperor's New Cloak", Kira killed Brunt. This cycle is perpetuated in the Star Trek Customizable Card Game where each successive death can enable the player to bring into the game the next person in the cycle (i.e. Quark downloads Rom, Rom downloads Nog, etc). The cycle can also be looped, in that Brunt (the last person to die) can download Quark and start it all over again.

...that throughout the entire Deep Space Nine series, Quark has killed Jem'Hadar soldiers on three different occasions? (DS9: "The Jem'Hadar", "Sacrifice of Angels", "The Siege of AR-558")

...that Sito Jaxa, presumed killed in The Next Generation episode "Lower Decks", was at one point intended to turn up alive in an episode of Deep Space Nine? The proposed story would have found Sito in a Cardassian prison and would have climaxed with her killing her own cellmate.