David Shephard was the son of divorced parents Jack Shephard and Juliet Burke (whom he lived with), in the flash sideways. He was a gifted pianist. His relationship with Jack was strained, due to their misconstrued expectations of each other. In the original timeline, Juliet never raised a son, and, to his knowledge, Jack never had one either.
David first appeared after Jack's return to Los Angeles, when Jack picked him up at St. Mary's Academy. Back at his apartment, Jack tried to converse with his son, but it ended awkwardly. He tried to talk to David about The Annotated Alice, which was lying in his room, but David just walked out of his room. Later, David opted to stay alone in the apartment while Jack went to visit his mother, Margo. Jack asked his mother how she viewed his relationship with David, and she replied that David might just be terrified of him. She noted that David was also visibly upset during Christian (his grandfather)'s funeral. ("Lighthouse")
Upon returning home, Jack found his son gone. He went to his ex-wife's house to see if David was there, but found nobody home. Still, he went inside and into David's room, where he came across sheet music for Chopin's "Fantaisie Impromptu", and pictures of himself and David on the mirror. Jack listened to the two messages on the answering machine. The first was from the Williams Conservatory confirming David's slot at 7:00pm on Friday the 24th. The other was a message from Jack himself, from Sydney. Jack looked at his watch and realized the audition must have been taking place right then. ("Lighthouse")
Jack arrived at the conservatory, where he saw David playing the piano. A boy commented on how talented David was, while his father told Jack "They are too young to have this kind of pressure,". The boy's father referred to David's "gift." Afterwards, outside, Jack asked David why he had never told him that he was still playing music, to which David replied that he didn't want "to fail" in his father's eyes. Jack relayed how bad his own father made had him feel, and told David he never wanted him to feel that way, that he loved him and that, in his eyes, David could never fail. ("Lighthouse")
A day or two later, David went with his father for the reading of his grandfather's will and testament. There, they were introduced by the lawyer to Claire Littleton, who told them she was Jack's half-sister (and thus David's half-aunt). An emergency at the St. Sebastian Hospital required father and son to leave abruptly, but Jack invited "Aunt Claire" to stay with them. ("The Last Recruit")
The next morning, David announced that he'd made breakfast for them, and Jack joked that "opening a box of cereal is not making breakfast," indicating a marked improvement in the father/son relationship. David reminded Jack about the benefit concert that night, Claire joined them for breakfast, and an alleged Oceanic Airlines representative called to say that Christian's casket had been found. ("What They Died For")
David was later seen at the hospital where his father and mother Juliet, both worked. He asked who would use Jack's ticket now that Jack had to perform surgery. Jack suggested Claire; David and Juliet agreed. At the concert venue, Juliet had to leave for a hospital emergency, then Claire went into labor and Kate (also at the table), followed, thus leaving David alone. ("The End") David is never shown again after this.
- Among the main characters, David only met Jack, Juliet, Claire, Ilana, Kate, Charlie, Daniel, Desmond, Christian and Sawyer.
- David was an LA Dodgers fan (he was seen wearing an LA Dodgers Hat) unlike his dad, Jack, and grandfather, Christian Shephard, both fans of the Boston Red Sox. ("Lighthouse")
- Judeo-Christian tradition holds that a "shepherd" boy named David (who also was a gifted musician) was the only person in Judea brave enough to fight the giant Goliath. He won against improbable odds and became the king of Judea. The most famous Psalm of David, Number 23, opens with the line, "The Lord is my shepherd."
- In 2014 fantasy-comedy movie Alexander and the Terrible, Horrible, No Good, Very Bad Day, actor Dylan Minnette has portrayed a character named "Anthony Cooper", which is the same name of a supporting character played by Kevin Tighe on Lost.
- David and his relationship with his father were foreshadowed in the mobisode, "The Watch", and perhaps in the episode "Something Nice Back Home".
- The piece that David played at the piano competition in "Lighthouse" was the same one that young Daniel Faraday was playing when his mother walked into the room, at the beginning of "The Variable." It was Fantaisie-Impromptu in C-sharp minor by Frédéric Chopin.
- For fan theories about these unanswered questions, see: David Shephard/Theories