The Thing You Love Most - S1-E2
Continuity mistake: When Emma is wearing the red dress in "Pilot", she has a mole on her chest. In this episode, which takes place two days later, when she's in her white tank top, the mole is gone; this is best seen when Graham is taking mug shots of Emma, and she says "He's terrified of her, like everyone else in this town." This is probably due to the fact that in real life, Jennifer Morrison has had several moles removed from her body. However, there was no time for Emma to do the same, and even if there were, she'd have a fresh scar or stitches. (00:20:30)
The Thing You Love Most - S1-E2
Continuity mistake: In the beginning of the episode, as Regina stops below the clock tower and gazes at the clock, there is no sign on the blue building in the background, next to Storybrooke Country Bread. When she notices Emma's car, there is a sign on the building. (02:55:00)
Snow Falls - S1-E3
Continuity mistake: As the trolls search through Prince Charming's belongings, one of them is seen pulling out Snow White's wanted poster from the bag, but in the previous overhead shots, he was already holding it in his hands. (00:27:45)
Continuity mistake: As Ashley tries to break into Mr. Gold's safe, which is hidden behind a painting, in the first shot, she's moving the painting with her left hand. In the next shot, her right hand is up by the painting, and the lever on the safe has changed position, even though there was no time to turn it. (00:09:55)
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)
Continuity mistake: The feathers in the enchanted quill that Cinderella gives Rumplestiltskin keep going from being smooth and even to being frayed between shots. (00:28:55)
Continuity mistake: When Ashley is holding baby Alexandra while Emma comes in, her left hand repeatedly changes position between shots; for example, when Emma says "It's pretty", her hand is on one side of the baby's head; in the next shot, it is on the other side. (00:36:25)
Continuity mistake: After Henry runs up the stairs, he puts his backpack on the bed, with the backside facing upwards. When he takes off his shoe and throws it on the floor, the top of the backpack is facing upwards. When Regina enters his bedroom, the backside is facing up again. (00:38:35)
Continuity mistake: When Henry lies on the bed, the position of his legs goes from one leg being crossed over the other, to being parallel to each other, between shots. (00:38:40)
Continuity mistake: When Sean is visiting Ashley at the hospital, as he says "Yeah, I'm back", baby Alexandra is waving her tiny hands in the air. In the previous and following shots, her hands are down. (00:39:10)
That Still Small Voice - S1-E5
Continuity mistake: During Henry's first therapy session, as Archie says "So all the crickets in Storybrooke, they were once people too?", Archie's holding a coffee cup in his hand. In the next shot, the cup is sitting on the table. (00:02:45)
That Still Small Voice - S1-E5
Continuity mistake: After Regina tells Emma to clear the crowd away after Henry is rescued from the collapsed mine, Regina's hand goes from being on Henry's face to his side/waist between shots. (00:34:35)
The Shepherd - S1-E6
Continuity mistake: When the twin brother is getting ready to slay the dragon, you can see the scar on his face which hasn't happened yet. In scenes before and after, the scar is not visible. (00:24:00)
The Shepherd - S1-E6
Continuity mistake: When Mary Margaret is sitting at the bar with Doctor Whale, the straw and lemon slice in the empty drink in front of her keep changing position between shots. (00:39:40)
The Heart is a Lonely Hunter - S1-E7
Continuity mistake: When Graham is arguing with Emma at the beginning of the episode, in the very first shot outside Granny's, they are approaching a shop called Worthington's Haberdashery. As the shot ends, they are still a few meters away from it, but in the next shot, they are already in front of it. (00:01:50)
The Heart is a Lonely Hunter - S1-E7
Continuity mistake: When Emma is talking to Mary Margaret in the morning, as Emma says "Tell me, what do I do?", Mary Margaret's left hand jumps from the bowl of sugar to her teacup between shots. (00:09:40)
The Heart is a Lonely Hunter - S1-E7
Continuity mistake: In beginning of the scene where Regina pays a visit to the Sheriff Department, the darts on and around the dartboard change position between the close-up of the dartboard, and the wide shot where Emma bends down to pick up a dart. (00:22:05)
The Heart is a Lonely Hunter - S1-E7
Continuity mistake: As Emma exits the crypt, in the wide shot, Regina's left hand, holding the flowers for her father's grave, is at her waist. In the next shot, her hand is down by her side, before she brings it up to show the flowers. (00:33:35)
The Heart is a Lonely Hunter - S1-E7
Continuity mistake: After Emma punches Regina, Regina has a wound by her mouth. For the rest of the episode, the wound keeps changing appearance and position. (00:34:40)
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)
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.