The debate rages on about whether David represents Christian, Aaron or Jack himself -- or whether David really is Christian, Aaron or Jack himself. This debate sadly ignores far more convincing theories about who David really is.
David is Dave
Everything you need to know about the flash sideways is right there in "Dave". A fake reality based on the real life you lived? Check. Imaginary figures whose existence inhibits your moving on? Check. And how do you escape this phoney world? Let's ask Dave.
HURLEY: So I'm making you up?
DAVE: Well, sort of. I'm part of your subconscious, man. All the people on this island are.
HURLEY: What part of me are you?
DAVE: I'm the part of you that wants to wake up, man. Follow me.
[We see them arrive at a high cliff above the ocean.]
DAVE: This is it, dude.
DAVE: The big finale. The answer to all your problems. A way for you to wake up, snap out of it.
HURLEY: I don't want to kill myself.
DAVE: Who said anything about killing yourself, man? This is going to bring you back to life. The only way for you to bust out is to tell your mind that you don't believe any of this.
HURLEY: So, if I -- all this will be gone? I'll just wake up?
DAVE: That's right. And when you do wake up, come find me. I'm sure I miss you. See you in another life, Hurley.
And besides the simple fact that these imaginary friends share a name, we have one other important factor linking them: they make you eat.
Yes. Bet you thought Jack's issues involved his father or fixing people. Not so. According to the flash sideways, Jack's subconsciousness revolved around food, and David existed to further this obsession.
- Jack's brings David to his place. He tries to initiate a conversation, but David leaves and goes to... the fridge.
- Minutes later, Jack invites him to Margo's. David refuses the invitation in favor of Pepperidge Farm cookies.
- Jack comes home with beer (?!) and pizza. David is nowhere to be found. Jack mourns the waste of pizza.
- When the two talk after the audition, we see no smiles. Till Jack mentions dinner. Then they leave happily.
- The next time we see the two, Jack tries to palm off David with Juliet. David, furious, nudges his father. Jack agrees to keep him longer... so they can get something to eat.
- At Jack's place, David makes breakfast. Opening a box of cereal doesn't count as making breakfast, says Jack, but David insists that it does. Then Claire enters, and they all eat together, resulting in the creepiest brother-sister scene since Boone and Shannon went down under.
- David's final scenes involve him trying to drag his dad to a dinner. When the dinner finishes and the concert begins, David's use in the flash sideways ends. He vanishes.
David is Squirrel Baby
The season 6 soundtrack exceeded my expectations in all ways. But I still never thought it would reveal show secrets... yet it did. The track Peculiar Parenting was not just Jack's flash sideways theme, as I thought it would be. It also contained Clarriseau's motif.
Jack and Claire - two peculiar parents both imagined children. And in both odd relationships, at least one member was dead.
I think squirrel baby is likely a character that exists in all possible worlds. It travels between universes, relieving parents who have suffered loss.
David is Libby's husband
When Libby's husband left her. She went crazy. Rewatch the scene where she explains it to Desmond. It seems oddly familiar. We see a woman react to loss that way some other time... Aaron's adoptive flash sideways mother, who cried when her husband moved on without her.
Who's to say that children in the flash sideways don't go to our world when they die? They then live in an obviously false reality, where ghost whisperers advertise openly and planes vanish into thin air. I think it's almost certain that Libby's husband eventually remembered his true life, his life in the flash sideways that he spent with Student. The two moved on together, leaving Libby to -- justifiably! -- question whether her world was real at all. Time to check into Santa Rosa.
David is Frank
Consider all the evidence:
- Both are accomplished pianists. We never saw Frank play the piano, but we know he did.
- Both are white. As the Abaddon=Walt theorists proved, this matters.
- Team affiliation. Jack set up the TV so David could watch the Sox. But David, according to pictures in his room, was a Dodgers fan. Reasonable if he really lived in L.A., but bizarre if David were a manifestation of Jack's subconsciousness and Jack's mind manufactured the scene in his room. Why would Jack imagine David hanging smiling photos of the two of them together but then tack the Dodgers in there? Only one possible answer exists: David was Frank, who bled Yankee blue. His Sox hatred bled into the afterlife, and Jack rationalized it as a love for the L.A. Dodgers
- Hair. When we first see Frank, he as a full beard. When we next see him, he has shaved. When we next see him, clearly he would have shaved his entire body and regressed into a boy.
- Jack's last words to Frank in season 4 were "I hope we never see each other again." Frank replied, "Roger that, Doc" and laughed. His way of saying "Even death cannot save you from me."
David is Sarah Shephard's lover
But what of his troubled marriage to Sarah? He transformed it into a healthy post-marital relationship with Juliet? With no trouble at all? Doesn't sound like the sort of thing Jack would manage.
David is most likely Sarah's lover, haunting Jack even in the next world. Look at all the parallels.
- Jack spent long periods on the phone, calling numbers to get in touch with both.
- Worrying about both caused Jack to drink.
- Fans theorized that both were Christian.
- Both result in one of Jack's ex-wives getting pregnant.
And most damning of all, are Sarah's words to Jack about the lover's identity: "It doesn't matter who he is! It just matters who you're not!"
Same with David.