Continuity mistake: When Archie's friends are gathered in Mary Margaret's apartment after the funeral, the cutlery in the bowls of salad moves around between shots when Ruby is talking. (00:12:50)
Continuity mistake: When Mr. Gold and Belle are walking to the pawnshop together, their position in relation to the storefronts they walk past keeps changing. Most notably, they walk past a couple of wheelbarrows three times in consecutive shots. (00:13:35)
Continuity mistake: When Belle is looking for Baelfire's shawl and distractedly sets down the gun, the gun keeps changing position on the bench. (00:24:00)
Continuity mistake: Aboard The Jolly Roger, Baelfire's shawl, on the bench, changes position between the close-up and the wide-shot when Hook puts it down. The shawl changes position again between when he says "Now, what makes you think you are any different?", and when Belle grabs it. (00:26:10)
Revealing mistake: When Belle hits Hook with a rowing paddle, as he falls into the hatch, you can see the face of Colin O'Donoghue's stunt double. (00:28:10)
In the Name of the Brother - S2-E12
Continuity mistake: In the opening scene, the amount of blood on Hook's face and neck from the car accident keeps changing. (00:00:30)
In the Name of the Brother - S2-E12
Continuity mistake: While Hook lies off the side of the road in agony, the position of his arms keeps changing between close-ups and wide shots; this can be seen when the police arrive and Emma finds him. (00:00:30)
In the Name of the Brother - S2-E12
Continuity mistake: When Belle is holding the chipped cup, the cup turns around in her hands when Gold says "It's your talisman." The same thing happens when she tries to give it back to him. (00:34:20)
Continuity mistake: When Belle is watching TV at the Storybrooke hospital, her hair, hanging in front of her shoulders, changes position between the wide shots and the close-ups. (00:10:20)
Continuity mistake: At the airport, while Emma is standing in line at the security checkpoint, the way her red scarf is tied around her neck changes a couple of times, and the creases in the scarf repeatedly change between shots. (00:16:00)
Continuity mistake: When Anton is trapped in the hole, right before Charming exits his car, there is a shot of Anton clinging to the pipe, where you can see the rope they will use to rescue him, dangling next to him; even though the rope hasn't been lowered down yet. (00:20:40)
Continuity mistake: On the plane, Henry is eating baked goods from Cinnabon's. The size and position of the stains of frosting inside the box changes after he says "The only thing that could make this day any better, is more frosting." (00:40:25)
Continuity mistake: While Emma is talking to Mary Margaret on the phone, an extra (lady with a purple shopping bag) comes from behind Emma. The scene then switches to Mary Margaret, then back to Emma, and we see the exact same extra walking behind her again. (00:14:40)
Continuity mistake: When David is making breakfast, he turns around, with a frying pan full of pancakes in his hands. In the next shot, he begins to lift up a pancake with a spatula, but when it cuts, he's already holding it out. (00:03:15)
Continuity mistake: After Mary Margaret opens the birthday present from Johanna, the wrapping, lying around the present, changes position a couple of times. (00:03:55)
Revealing mistake: When Hook attacks Mr. Gold, if you watch as he pushes Emma out of the way, you can easily see that one who actually pushes Jennifer Morrison is Colin O'Donoghue's stunt double. When Hook pushes Mr. Gold against the security gate, it is the stunt double who pushes Robert Carlyle. (00:18:25)
The Miller's Daughter - S2-E16
Visible crew/equipment: When Rumpelstiltskin goes to Cora as she is trying on her wedding dress, as he sits down on the chair behind her, you can see the tape used to mark the spot on the floor - it's bright red and in an X shape. (00:24:39)
Welcome to Storybrooke - S2-E17
Continuity mistake: When Emma is having breakfast, the amount of cereal in the bowl in front of her keeps changing. (00:09:55)
Welcome to Storybrooke - S2-E17
Continuity mistake: During breakfast in Mary Margaret's apartment, there are two plates of toast on the bench. The distance between the plates changes between different camera angles. In some shots, they are right next to each other; in others, there is a gap of approximately 30 centimeters between them. (00:09:55)
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.