The Irving Berlin standard that Data sings at the wedding of William Riker and Deanna Troi in Star Trek Nemesis, and which later becomes a recurring memory of him in Star Trek: Picard.
Blue Skies is a twentieth-century Earth song by Irving Berlin. In Star Trek Nemesis, set in 2379, Data performs it as his gift to the bride and groom at the wedding reception of Riker and Troi in Alaska, to Worf's evident discomfort.
After Data sacrifices himself to destroy Shinzon's ship, his memories survive only as a download in the simpler prototype B-4. In the film's last scene B-4 begins haltingly to sing the song, a hint to Picard that something of his friend remains.
Star Trek: Picard takes up the thread. Remembrance opens with a recording of the song over a dream of a poker game with Data, and in Et in Arcadia Ego, Part 2 it is sung again as Picard honours Data's wish and lets his preserved consciousness come to an end.