Morn is seen sitting at his usual spot at Quark's bar. The character, played by Mark Allen Shepherd in Star Trek: Deep Space Nine (1993), has now appeared in 96 television episodes of the Star Trek franchise, having never said a word onscreen.
The title of this episode, "Hear All, Trust Nothing", is the 190th Ferengi Rule of Acquisition.
As the Cerritos circles the station, the soundtrack switches to the theme music for Star Trek: Deep Space Nine (1993). The opening credits to DS9 involves a POV from a ship circling the station multiple times - this is referenced by the crew.
Mariner says that without her, the other Lower Deckers would probably get lost on DS9 and end up in a mirror universe with "Smiley." Smiley was the nickname of the mirror universe counterpart of Chief Miles O'Brien, seen on numerous occasions throughout the Star Trek: Deep Space Nine (1993) series.
The baseball Kira is seen holding in her office is a reference to Captain Benjamin Sisko. It is presumably the same one he left behind in What You Leave Behind (1999).