Continuity mistake: When Milah and Killian board The Jolly Roger, as Milah says "Fetch some water", a pirate with a coil of rope around his arm has just ascended the deck and is seen near the steps. In the next shot, he is nowhere near that area (he can briefly be glimpsed as he disappears behind a mast in the lower left hand corner). (00:25:45)
Continuity mistake: When David and Rumplestiltskin walk down the streets of Storybrooke while searching for Belle, as David says "There is a difference between literal truth and honesty of the heart", a car is seen driving through the street. In the next shot, it's gone. (00:21:20)
Continuity mistake: When David and Rumplestiltskin are looking for Belle, when Rumple says "Look, can I ask you a question?", in the background, a man and a woman are crossing the street. In the next shot, they cross the street again. (00:20:40)
Continuity mistake: When Rumpelstiltskin and David are out looking for Belle, they cross the street, and for the rest of the scene, the pedestrians change from shot to shot. (00:20:55)
Continuity mistake: At Granny's, when Belle and Ruby chat, the slice of lemon and the straw in Belle's iced tea move around between different camera angles. The same thing happens to the straw in the half empty glass in front of her. (00:12:15)
We Are Both - S2-E2
Continuity mistake: After Mary Margaret is knocked out by Mulan and falls to the ground, the amount of straws and dirt on her clothes changes between shots. When she is thrown into the dungeon with Emma, her clothes are clean. (00:39:55)
Continuity mistake: After Prince Philip's body is placed on the bier, Mulan wraps the wraith's medallion in a bag and gives it to Aurora. In the wide shot, the strings on the bag are hanging over the left side of Mulan's hand. In the close-up, they are hanging down the right side. (00:33:25)
Continuity mistake: In the scene where Mulan and Aurora are alone in the forest and Mulan is trying to make a fire, she alternates between wearing her long ponytail over one shoulder, and letting it hang down her back. (00:24:45)
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: During Emma's sword fight with Hook, when Emma is on the ground, reaching for her sword, Hook sticks his own sword into the sand so that he can drag her away from her weapon. Cuts to a different shot, and his sword is lying on the ground, near his feet. A couple of shots later, the sword is planted in the ground again. (00:27:55)
Audio problem: At Lake Nostos, when Mulan gives her magical sword to Mary Margaret, in the shot before she says "It deflects her magic", you can se her jaw moving as if she's talking, but nothing is heard. (00:28:40)
Continuity mistake: After Hook throws the satchel that holds Aurora's heart to Mulan, the way she holds the satchel keeps changing; most noticeably, in some shots, she's holding it by the straps, in others, the satchel is lying in her hand. (00:28:20)
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)
Tallahassee - S2-E6
Continuity mistake: When Hook and Emma find the skeleton of Jack the Giant Killer, in the close-up shot, Jack's sword is in the skeleton's hand. When Emma remarks, "With that toothpick?", the sword is lying beside the hand. When Emma grabs the sword while being chased by the giant, the sword is back in Jack's hand. In addition, the skeleton's arm alternates between being bent and sticking straight out between shots. (00:23:15)
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.