Continuity mistake: When Graham offers Emma the job as a deputy sheriff, when he gives her his card, you can see two women a few meters behind Emma, walking on the pavement, toward the camera. In the next shot of Emma, only a few seconds later, the women are still walking in the same direction, but they are much further away from her than in the previous shot. (00:16:15)
The Thing You Love Most - S1-E2
Continuity mistake: When Regina picks up Malificent's staff, Lana Parilla's black feather tattoo is visible on her right wrist. The tattoo can also be glimpsed when Regina bangs a gavel to start the meeting at the Storybrooke Town Hall in "Fruit of the Poisonous Tree." For the rest of the series, the tattoo is missing. For example, when Regina hands Emma a drink in "Pilot", when she tries to burn the book of spells in "We Are Both", and when she tries to make a potion in "Witch Hunt", her wrist is bare, and there is no tattoo. (00:07:25)
Continuity mistake: In "That Still Small Voice", when Regina throws the piece of glass down the shaft, it lands on the rest of Snow White's glass coffin, which has several holes in it. When Emma finds the coffin in this episode, there is only a single hole in the glass, and the ends of the coffin (made of wood), are much smaller. (00:20:15)
The Heart is a Lonely Hunter - S1-E7
Continuity mistake: When Emma is with Graham at the Sheriff's office at the end of the episode, her hair keeps changing. For example, in some shots, there is a lock of hair hanging down the left side of her head. In others, it is tucked behind her ear. (00:36:15)
The Heart is a Lonely Hunter - S1-E7
Continuity mistake: When Emma is pressing an ice pack to the wound that Regina gave her, her bracelets repeatedly move up/down her arm between shots. (00:36:25)
An Apple Red as Blood - S1-E21
Continuity mistake: When Regina offers Jefferson a drink, he declines by dropping the white rabbit card in the glass. In the next shot, the card is gone. (00:12:55)
Continuity mistake: When Emma wakes up on Jefferson's couch, her left tank top strap changes position between shots: First, it's at the edge of her shoulder. When she sits up, it's off her shoulder. In the next shot, it's on top of her shoulder, before moving back to the edge of her shoulder in the following shot. A couple of shots later, it's at the top of her shoulder, even though her hands are tied behind her back, and she could not have moved it. (00:10:20)
Continuity mistake: When Emma and August are walking down the streets of Storybrooke in the morning, in the first shot, they are walking past Storybrooke Dental. Cuts to another shot, and they are now walking next to the Clock Tower building. As the shot ends, they are walking past a window covered in newspapers. In the next shot, they walk past the very same window again. Cuts to another shot, and they have suddenly walked past the building as they are crossing the street. (00:01:20)
Red-Handed - S1-E15
Continuity mistake: When David is interviewed at the sheriff's station, after Emma says "And honestly, liars have better material", her left thumb is resting on the edge of the coffee cup in her hand. In the next shot, it's not. (00:01:20)
Continuity mistake: After the door to door candle sales fail, when Leroy is about to deliver the bad news to Astrid, the position of Mary Margaret's coat, which she's holding in her arms, changes between shots. (00:21:00)
Continuity mistake: When Astrid accidentally dumps glitter on Leroy, in the first shot, there's hardly any glitter on him. Cuts to the next shot, and he is covered in glitter. The amount of glitter on his clothes repeatedly changes for the rest of the scene. (00:05:20)
Snow Falls - S1-E3
Revealing mistake: When Snow White steals one of the royal guards' horses, as she rides off, in the second shot, you can see that the one riding is not Ginnifer Goodwin, but her stunt double. When Prince Charming catches up to her and knocks her off her horse, Josh Dallas' and Ginnifer Goodwin's stunt doubles can both be seen. (00:03:55)
Continuity mistake: The way the baby blanket is wrapped around the infant Emma repeatedly changes between shots. For example, as Charming approaches the magical wardrobe, the blanket has just a tiny opening over the baby's face, and the embroidery with Emma's name on it is showing; in the next shot, the opening is much bigger, and the embroidery can no longer be seen. (00:30:00)
Continuity mistake: When David is having dinner with Regina, as Regina says "How did you like it?" her left hand is lying on the table. In the next shot, her hand is under her chin. (00:20:55)
Continuity mistake: When David is carrying Regina's groceries, there's a plastic bread bag sticking out of one of the grocery bags. The amount of plastic sticking up repeatedly changes between shots. (00:15:45)
Continuity mistake: When Regina is standing by the tree with Daniel, as she says "Have you not seen her magic?" Rocinante, Regina's beloved horse, is standing next to them. In the following wideshot, Rocinante is nowhere to be seen, and there was not enough time to move away from them. (00:08:05)
Continuity mistake: When Regina first kisses Daniel, her head is tilted to the left. In the next shot, her head is tilted to the right. (00:05:05)
Continuity mistake: In the Queen of Heart's maze, when Regina closes the hedge to entrap the pursuers, the spears sticking out from the leaves change position between the wide shot and the close-up. (00:26:10)
Continuity mistake: When the Mad Hatter and The Evil Queen are in the portal of doors, on the left side of the mirror, there's a door with green curtains. The design of the curtains changes between wide shots and the shot where they enter Wonderland. Most notably, in the wide shots, the curtains have brown edges, but when they are standing in front of the mirror, the edges are green. (00:15:55)
Red-Handed - S1-E15
Continuity mistake: In the scene where Ruby reconciles with Granny, in some shots, her necklace is tucked into her clothes. In other shots, it's outside her clothes. (00:36:25)
Answer: He knows who she is because he knows that the fairy tales are true. He was also shown to sneak out to go see Emma or someone else. Sometimes he succeeded, sometimes he didn't. This is how he knew to look for her despite his strict mother.