At the end of the episode, Odo has sent everyone affected by the telepathic matrix to a cargo bay. Sisko and O'Brien remove their com badges, throwing them aside before heading to the bay. After everyone is cured, Sisko straightens back up and, in the closeup, you can see that he has a badge on. In the next closeup, it's gone again.
Buck Bokai, a baseball player from the 21st Century, who becomes "real" in this episode, broke Joe DiMaggio's consecutive hitting streak in 2026. While he's not physically seen or referred to by name, this fact is mentioned in the 'Star Trek: The Next Generation' episode "The Big Goodbye."