In "The Bounty," Riker, Worf (Michael Dorn), and Raffi Musiker (Michelle Hurd) are searching for a project manifest on the Daystrom Institute's Daystrom Station, but they're watching out for a dangerous AI that's protecting it. A raven hologram suddenly appears, and the trio then hears music as a Professor Moriarty (Daniel Davis) hologram attacks them.
He explains that the music is stuck in his head, and that's when Riker remembers walking through the holodeck forest in "Encounter at Farpoint." He puts the pieces together and whistles the end of "Pop Goes the Weasel." Professor Moriarty then disappears, clearing the way for them to come face-to-face with an AI that appears to be Data.
While "Pop Goes the Weasel" is a callback to the series premiere of "The Next Generation," Data dreams about a raven in Season 6, Episode 16, "Birthright, Part I," and Professor Moriarty is a foe that Data first encounters in Season 2, Episode 3, "Elementary, Dear Data." Each of these three clues adds anticipation and emotion to this reunion in "Picard.