Season 3, Episode 21:
As Emma becomes more and more convinced she needs to flee Storybrooke with Henry, Zelena's time portal reopens, and investigating it ends up pulling her and Hook in. In the Enchanted Forest of thirty years ago, Emma accidentally stops her parents from meeting, and sets off a chain of events that could risk her not existing. While Rumplestiltskin aids them in figuring out a way to reopen the portal, Emma and Hook must find a way to get history back on track.
- Back for the Finale: Abigail/Kathryn and Midas. Interestingly, both of them come off a bit more jerkishly than they did originally, but Midas is merely toeing the party line as far as Snow White is concerned to keep Regina from becoming his enemy too while Abigail is quite clearly still suffering under the resentment of the Arranged Marriage keeping her from finding a way to bring Frederick back. Oh, and Blackbeard appears just to prove what a scoundrel he is again.
- Black Comedy: Grumpy, talking about what would have happened to Aurora's baby if she hadn't been turned back from a Winged Monkey in time.
- Cliffhanger: Naturally for a two-parter: Emma is arrested by Regina for aiding Snow White.
- Continuity Nod: Hook stops Smee from killing a rat because "you'll get it later."
- Contrived Coincidence: Kathryn's reintroduction just so happens to require Snow and Charming to explain about their connection to her to Hook, who is not familiar with her...so that when he and Emma end up in the past, they'll know who she is and what has to be done to put history back on track.
- Dances and Balls: Emma comments on how much her mother went on about them and not getting what makes them so special. Once she's actually there and sees what it's like, she changes her tune. (Helped by getting to have a Dance of Romance with Hook.)
- Dramatic Irony:
- If Emma hadn't been worried that David was calling about her walking out of the diner and planning to leave Storybrooke, she would have answered her phone and found out about the time portal sooner and stayed away—by the time she does get his text, they're too close to escape.
- Regina was the one responsible for imprisoning (and eventually executing) Marian. Contrasted by her sincere sorrow when Robin Hood tells her some of the story, since at the time she had no idea who the woman she'd executed was.
- After going to all the trouble of getting Snow to the ball to steal the ring, she ends up dropping it when fleeing from Charming, so that Emma ends up with it and still has to get it back to her parents.
- Driven to Suicide: Gold alters the security camera footage to make it look like Zelena did this.
- Glamour: Rumpelstiltskin uses this to disguise Hook and Emma so they can enter Midas's ball and ensure Snow and Charming meet.
- Idiot Ball: So Emma, you say you want to escape Storybrooke and be free of all the danger and evil magic. But what's the first thing you do when you see a giant pillar of light exploding into the sky? Go to investigate. When you no longer have magic. (Also, about that "I'm not a hero/the Savior" thing...)
- I Hate Past Me: While it's clear as soon as he sets eyes on him that Hook disapproves of his past self's drunken dissipation and roguish ways, it's not until he witnesses him kissing and trying to seduce Emma that he punches his lights out.
- I'm Mr. [Future Pop Culture Reference]: Needing pseudonyms at the ball, Emma introduces Hook and herself as Prince Charles and Princess Leia. Since no one in the Enchanted Forest yet knows of Earth, these are actually very safe aliases to use, but still hilarious. (The latter is even funnier in hindsight considering Disney's deal with Lucasfilm...) On the other hand, forgetfully mentioning things from the future she shouldn't (like Belle and Rumple getting together, or calling Regina by name) is more problematic.
- In the Past, Everyone Will Be Famous: As soon as Emma and Hook orient themselves, who do they find themselves near? Regina, paying a visit to a village where Geppetto and Granny happen to be. And not long after this they encounter Charming and Snow.
- It's All About Me: While she has justifiable reasons, Emma is being rather selfish when insisting on fleeing to New York and that this would be best for Henry. Hook calls her on it actually being about her desires and fears.
- Male Gaze: Hook has a hard time keeping his eyes on Emma's face when she steps out in her Enchanted Forest garb.
- Meaningful Name: The episode title. It's a parallel to Season 1's "Snow Falls" because it involves Hook and Emma living through the same events, but the name change also suggests how Emma's inadvertent action is changing history, causing the timeline to "drift".
- Never the Selves Shall Meet: At first, naturally enough, Emma and Hook do all they can to make sure the two pirate captains don't meet while they set up Snow White's robbery of Charming. When Past!Hook insists on taking Emma back to his ship or else he'll leave her, Emma has no choice but to go along—and do all she can to keep him from seeing both Snow and Future!Hook, while poor Smee gets very confused. Just as Future!Hook is about to escape, he ends up punching out his past self—because, as he says, he won't remember any of it thanks to the rum.
- Newspaper Dating: Variation—Emma identifies what time period they're in by seeing one of Snow White's wanted posters on a tree.
- Retcon: Robin Hood reveals that, contrary to what he'd said in "Witch Hunt", Marian was simply executed (though he didn't know it, for refusing to tell the Evil Queen where Snow White was, it turns out). Though it is possible that one of his heists led to her knowing where Snow White was and thus everything that followed (or he thought it did). Either way she seems to be quite the Unlucky Extra.
- Ripple Effect Indicator: The storybook becomes this once Emma interferes with the timeline. Lampshaded and discussed by Rumplestiltskin.
- Set Right What Once Went Wrong: The whole premise of what happens once Emma accidentally makes it so her parents never meet. Unfortunately even as some things get fixed, other things get more out of whack...
- To Back to the Future. Emma first thinks she is Marty McFly, confusing Hook. Then she actually does stop her parents from meeting, setting up a similar plot of getting them to meet again.
- Aside from the Star Wars reference above, when David and Mary Margaret talk about a coronation presentation for their baby, Emma asks if they intend to do it like in The Lion King.
- Show Some Leg: Emma has to provide a distraction by getting Past!Hook drunk and flirting with him. Once he gets insistent about going back to the Jolly Roger, it turns into an outright Kiss of Distraction situation.
- Unwitting Instigator of Doom: Gold —by getting his revenge on Zelena he left her magic pendant "without a tether" which caused the magic to seek out and try to bring about her last wish.
- Whole Plot Reference: It's Back to the Future in the Enchanted Forest, with Marty McFly being replaced by Emma and Doc Brown becoming Rumpelstiltskin. Just like Marty, Emma's accidental change to the timeline involves one of her parents falling out of a tree. And just like Marty, Emma's only chance to fix the timeline involves having her parents meet at a rhythmic ceremonial ritual.
- You Have to Believe Me!: Subverted; Rumpelstiltskin believes Emma when she says they're from the future because she has knowledge of him, Bae, and the Dark Curse she couldn't have any other way.