Early-Installment Weirdness: "The Price of Gold". In retrospect Rumplestiltskin wanting Cinderella's baby doesn't make a lot of sense. Later episodes put strong emphasis on the fact he was a father who knew the pain of having your child ripped away from you and practically everything he did was part of a very long, complex gambit to get his son back.
Unless you consider that he never intended to take Cinderella's baby, and just needed Emma to think he did so she'd owe him a favor for letting Ashley keep her. Or he wanted to be captured and used her deal as a means of getting caught and be in that prison cell, apparently unable to harm anyone.
Or that, besides his precognition, it was a Secret Test of Character that Cinderella failed, badly. Recall how the exchange went:
Rumpelstiltskin: And you would trade your other child for...comfort? Cinderella: I can always have more children.
At the end of Season 1, Emma and Regina, in order to save Henry.
In Season 2, and lampshaded, Regina tells Gold he will help her because of the one person they both don't want in their new world: Cora.
Pretty much everyone against Greg and Tamara in the Season 2 climax. They are planning on destroying Storybrooke, and when that fails, they abduct Henry and take him to Neverland, resulting in Regina, Rumplestiltskin and Hook allying with Emma, Charming and Snow to save Henry. This new-found alliance continues on in Season 3, albeit somewhat-grudgingly, as they work on rescuing Henry from Peter Pan.
Ensemble Cast: Even though Emma is supposed to be the lead protagonist, each of the primary characters, as well as some secondary and minor characters, share a good amount of screentime and each of their backgrounds are focal points throughout the series.
Enthralling Siren: One appears in "What Happened to Frederick" and attempts to seduce Prince Charming under the guise of Snow White.
Ermine Cape Effect: Justified in that it's a Fairy Tale world, but it's still odd that Snow's father, a king, is just wandering down the beach in fancy silks, fur, and a crown when he stops to pick up some rubbish (a magic lamp, but still).
Equivalent Exchange: According to Rumplestiltskin, all magic comes at a price. One of the most memorable cases was when he brought magic to Storybrooke. The price was that no one could leave the town without losing their memories. The whole reason he wrote the curse was to find his son, and now he's trapped thanks to his own dependence on magic.
Establishing Series Moment: Although the series had some major publicity behind it spoiling the premise, the tone of the flashbacks is established the moment the evil queen storms in, and it's Snow White who pulls a sword on her. A set up to the "unconventional retelling" tone the flashbacks will have.
The witch, Maleficent, considers the Dark Curse to be too evil and traded the Evil Queen for it specifically so no one could use it.
Hook, despicable as some of his actions may be, does adhere to some sort of personal code. Despite taking Aurora's heart, he's uncomfortable with the idea of her being permanently without it. So after he accomplishes what he wants with the item, he ensures that it gets returned to Aurora as it's "good form."
In "The Queen is Dead", Regina is visibly horrified when Cora reveals that she was responsible for the death of Snow White's mother just to manipulate Regina's life so that she becomes Queen.
Mr. Gold wants Emma elected Sheriff. So, he sets fire to Regina's office while Emma's there to rescue her, thus making her a hero. When she exposes his plot to prove a point to Henry about good over evil, it plays into his hands again and ensures her election. The citizens fear Regina, but they're terrified of Mr. Gold.
Regina, on the other hand, has to change the game. Her plan was successful only after she used Mr. Glass as a poisonous influence to push Emma to play by Regina's rules. Anytime Emma makes the right choice, she has an advantage against Regina.
Evil-Detecting Dog: Pongo starts barking at Regina when she waltzes into Dr. Hopper's office. That's because it's Cora in disguise as her own daughter. In a subversion, he doesn't even bark at Mr. Gold when brought to his shop or even the real Regina. Perhaps because at that point, Gold and Regina aren't truly evil any more.
Evil Feels Good: Or at least immaturity feels good. By encouraging them to be very naughty and playful seems to be how Peter Pan converts his boys into his warriors.
Evil Versus Evil: Happens alot between Regina/Evil Queen and Mr. Gold/Rumplestiltskin.
Regina and Cora (her mother) are very antagonistic, although they do later rekindle their relationship to become a Big Bad Duumvirate in Season 2.
Rumpelstiltskin and Captain Hook are mortal enemies.
Greg and Tamara vs Regina. This trope is even said word-for-word in a promotional trailer.
Regina and Maleficent, and Regina and the Blind Witch from the Hansel and Gretel tale. In both cases, Regina wins.
Regina, Rumpelstiltskin AND Hook joining forces with the heroes to battle Peter Pan, the evilest of all.
Regina vs Zelena. Well, technically it's Evil vs Wicked, but the principle applies.
Eviler than Thou: Think Regina and Rumpelstiltskin are bad? Regina's mother and Rumple's father are worse.
The Wicked Witch as she herself says "The Queen may be evil but I'm wicked." Makes sense, considering they're apparently half-sisters.
Exact Eavesdropping: Mayor Regina arranges a conversation with Emma to make peace, then leads the latter to talk about how crazy Henry is, knowing that Henry will be showing up to overhear the conversation.
Mary Margaret just so happens to find Johanna near the spot where Cora and Regina are searching for Rumplestiltskin's dagger and discussing their plans to use said dagger to control him.
While Cora is trying to deal with the father of her child before marrying Leopold, Eva just happens to be hiding nearby listening in.
Regina wanted Gold to make "something tragic" to happen to Kathryn. Unfortunately for Regina, abduction, not just murder is "something tragic."
Mr. Gold is fond of this one; he uses it again when assuring Belle that he won't kill Regina. The wraith he's summoned will...or will devour her soul, a Fate Worse than Death.
And then once again when casting the protection spell on Charming and Snow. Regina won't be able to harm them in "this" land, but she can certainly take them to another one.
This was used against Rumplestiltskin by Cora. He had fallen for her and agreed to amend their deal to have him take their first born child instead of Cora's first born in general. Later, she didn't run off with him and stayed with Henry, to have his children. They would not be Rumple's to take as it wasn't Rumple who fathered them.
Cora's initial reaction when he proposed the deal makes even more sense as of 'Witch Hunt' when we find out that she had already given birth to and abandoned her first born. It is possible that her initial plan was to eventually tell Rumpel about Zelena. Of course he would have had to go to Oz to get her...
Excessive Evil Eyeshadow: The Evil Queen, in the Enchanted Forest; more understated on Regina. And nonexistent on Regina prior to her turning to evil.
Most of the Queen's forces wear black full face masks. Interestingly enough, as we learn more about the Queen and she becomes much more sympathetic, her goons start to reveal more of their faces. She even starts calling them by name!
Averted with King George's soldiers. Their headgear consists of nothing more than a chain-linked coif with the face wide-open.
The Queen of Heartsís soldiers in Wonderland have no faces. Also counts as a Visual Pun since they're not face cards.
Face Your Fears: Nightroot is a magical cure for fear and anxiety. It accomplishes this by creating a physical embodiment of your fears that comes after you until you either conquer the fear or it kills you. In the story of Rapunzel, this is the "witch" that keeps Rapunzel locked in the tower.
Fake Memories: The Dark Curse not only gave everyone in Storybrooke Identity Amnesia, but a "real world" background that never truly happened though they think it did. Averted with Regina and Mr. Gold, since the former enacted the curse and the latter created it. Also averted with August, since he escaped the curse by going through the wardrobe with Emma. Unfortunately played straight with Jefferson, who also does not suffer from amnesia; he remembers both a life in Storybrooke and the Enchanted Forest, and it drives him nearly mad.
Dr. Hopper: I would never betray the doctor-patient confidentiality. Regina: Doctor? Doctor... Need I remind you you got your Ph.D. from a curse?
Regina gave Emma and Henry the false memory that Emma never gave Henry up for adoption and they've been together the past 12 years, to replace the Storybrooke-related memories that disappeared once Regina cancelled out her curse to escape Pan's.
Fantastic Racism: Deconstructed. From the Fairy Tale characters' point of view, everyone stays in their role's pigeonhole, good people/creatures are always good, the bad are always bad, the two sides are always in conflict and good always wins. In filling in many of the backstories, particularly the Villains', the series is showing the implications this world view would have.
Mulan's village, as well as her entire kingdom, are based on ancient China while most of the Enchanted Forest is based on medieval Europe, though a majority of the English-speaking inhabitants possess American accents.
Even though Belle's kingdom looks as European as the rest of the Enchanted Forest, she, her lord father, and her former betrothed all speak with distinct Australian accents, though the area may be based on the equivalent of France in support of the original Beauty and the Beast fairy tale.
Both Aurora and Cora's kingdoms seemed to be associated with Russia and Spain respectively.
Dr. Frankenstein's world have aspects of 19th-century London, but Alice's universe plays it straight by being a separate London of its own that is continuously stuck in the Victorian era.
Regina tearing down Henry's wooden fortress is regarded as a breathtakingly evil act by just about everyone. While it was certainly unnecessary and mean-spirited, the reaction seems... excessive. This is ignoring the fact that she has done by far worse before this, the wooden fortress was structurally unsound due to damage by a storm, and she does build a new play structure for the children (though admittedly, that was part of a plan to screw over Emma). Henry is just about the only kid who isn't happy with the new play structure. And it never even turns up again.
Rumple killing the unicorn. Again, while certainly bad, the reaction seems excessive. Viewers got more bent out of shape over the unicorn than over Gaston, or the poor mute maid. Have unicorns even been confirmed to be sentient in this universe? In fairness, what happened to the maid and Gaston were played for laughs, albeit in a black comedy sort of way. The unicorn, on the other hand, was played for drama.
Filler: While the show has a strong continuity, two episodes however contribute little to the main storyline:
"Dreamy" deals with the titular dwarf's past, his love for the fairy Nova and Snow making amends for her affair with David.
"Child Of The Moon" gives a backstory to Red as well to werewolves and set up a murder mystery but both of which are forgotten by the next episode.
Regina does this to Archie in "The Cricket Game". Then she kills him - except she's Cora, magically disguised in order to frame her daughter, and the corpse left behind isn't Archie, because the real thing is being held prisoner in Hook's brig.
Ruby does this in "In the Name of the Brother", just before Dr. Whale attempts to jump off the docks.
Flat "What.": David's mother on hearing that Prince "James" will be forced to marry Midas's daughter.
Flynning: Strangely averted. Despite the lack of blood in the sword fights, there's not a whole lot of clanking of swords just for the hell of it. The Prince fights in a hack-and-slash manner you'd expect from someone trained in broadsword.
Force Field: Storybrooke has one. "Bad things happen" to anyone who tries to leave the town (except Henry and Emma). Henry believes it's just Emma and handwaves how he can leave the town saying that since he's only 10 he would have no other choice but to eventually return.
When magic does return, Sneezy is picked as the first one to cross the line to find out what happens. He loses all memory of being Sneezy and reverts to his Storybrooke persona.
Foregone Conclusion: In "Tallahassee", we see Jack's skeleton in the Giants' home. When Jack finally shows up in a flashback in "Tiny", it's easy to guess where she's headed.
Really, most of the flashback sequences. Since most of the characters eventually end up in Storybrooke, they're obviously not going to die, no matter how dire the circumstances. Any character who does not end up in Storybrooke (like Phillip, King Henry, Daniel, etc) is exempt from this rule.
The real Prince James: "Next time make sure I'm dead." Oops.
A quick one but in "Snow Falls" Graham says that the woods are "his world." Emma appears confused by this, but the audience sees why in "The Heart is a Lonely Hunter".
In Episode 4, Mr. Gold mentions to Emma that no one wants to see Ashley's baby born in jail. Episode 9 reveals that this is what happened to Henry.
The unicorn mobile from Episodes 1 and 6, the dolls that turn out to be Geppetto's parents from Episode 5, and the windmill from Episode 6 can first be seen in Mr. Gold's shop in Episode 4 before they're all properly used in the plot.
Only within the one episode, but Prince Charming waking Snow White from her cursed sleep is related twice during the finale, once in flashback and once by Mary Margaret reading to the unconscious Henry ... then Emma breaks both the same curse on him and the one on Storybrooke with True (Maternal) Love's Kiss.
Neal/Baelfire knows Hook, and how to sail his ship and should be a couple hundred years old. It turns out that yes, he was in Neverland and had been a part of Hook's crew for a period of time.
In early season two, Belle's father tries to have her pushed across the town line, so as to erase her memory of Rumplestiltskin. It doesn't work, but later in the season Hook shoots her, causing her to cross the line.
Early in season three, Neal mentions ruby slippers and Tinkerbell uses poppy dust. Guess which 'verse is involved in the next big plot arc?
Freudian Excuse: Rumplestiltskin's taking babies makes sense when you learn about Baelfire.
Regina spent her entire youth being forcefully molded by Cora to be just as evil and cruel as her, all while claiming she did it out of love. It was a miracle it took Cora killing her fiance in front of her to start Regina down her path of darkness. But even then she tried to stay good, only for Rumple to show up as her mentor and further drive her towards evil. Oh and her one good parent sat by and watched it all happen.
Funny Background Event: A variation. While Snow and Lancelot are at the table discussing the events of the curse and other important matters, Emma is sampling the food and deciding that she likes the drinks offered. Apparently, roasted chimera isn't as good as it sounds.
The season 3 winter finale episode "Going Home" demonstrates the hazards of filming in a real-life urban centre. While everyone is going nuts about the curse returning, and as Pan holds a large group of townspeople spellbound in the middle of the street, in the background pedestrians and traffic can be seen going about their business, just as normal. You can even see the flashing lights of an emergency vehicle at one point. This is not the first time this has occurred in the series, which is shot in a suburb of Vancouver, but it is particularly glaring - and funny - in the context of this episode.