Continuity mistake: When Red meets Quinn, the way her hood is draped over his arm changes throughout the scene. The same thing happens when Red is holding it afterward. After Quinn drops the hood, the way the garment is crumpled up on the ground changes between shots. (00:12:05)
Continuity mistake: When David is confronted by Albert Spencer at the diner, as David gets up, his glass of beer is almost empty. When he picks it up, the glass is half full. (00:05:15)
Continuity mistake: At Granny's, when Ruby is clearing tables and Billy startles her, the amount and position of the food on a plate changes between shots. The cup and the napkins also change position on the table. (00:02:35)
Continuity mistake: When Emma finds Snow White's glass coffin, there's a hole in the lid. In the overhead shot, the hole is rather small, but in the shot from inside the coffin, the size of the hole has changed dramatically. In the next shot, it is small again. (00:20:15)
An Apple Red as Blood - S1-E21
Continuity mistake: In Regina's dream, when she walks away from the dinner table to answer the doorbell, she is wearing black pants. When she is tied to the tree, her pants are grey. (00:01:05)
Continuity mistake: When Emma and August are walking down the street in the morning, as he says "Take the day off. Come with me, and I'll show you", behind them, a man and a woman can be seen crossing the street. In the next shot, the exact same couple crosses the street again. (00:01:50)
Continuity mistake: When Mary Margaret and Emma attack Cora, she vanishes into thin air. In the next shot, they run toward the portal, and their weapons have mysteriously disappeared. They were there in the previous shot, and there was no time to get rid of them, especially not Mary Margaret's quiver, which was strapped to her body. (00:30:50)
Continuity mistake: During the showdown at Lake Nostos, Mulan's long ponytail alternates between hanging down her back to being in front of her shoulder between shots. Emma's hair also keeps changing position. (00:27:30)
Continuity mistake: When Pinocchio takes baby Emma in his arms, in the first shot, her baby blanket is wrapped tight around her. In the next shot, it is wrapped in a completely different way, less tight, with huge folds and the purple bands are tied up differently. In the next shot, the blanket is tightly wrapped around her again. In addition, when Pinocchio finds Emma inside the tree trunk, the way the blanket is wrapped around the baby is different from the way it was when Charming sent her through the magical wardrobe in "Pilot." (00:29:50)
The Return - S1-E19
Continuity mistake: When Mr. Gold is talking to Dr. Hopper in his office, there's a box of tissues on the table. The amount of tissue paper sticking up from the box keeps changing between camera angles. (00:26:15)
Continuity mistake: The dove that Mary Margaret finds in the woods has white feathers with a reddish plume around its neck. When she releases the bird after the storm has passed, it is not the same dove. The dove that she releases is completely powder white, with a different colored beak. (00:12:20 - 00:29:40)
The Heart of the Truest Believer - S3-E1
Continuity mistake: After Neal wakes up on the bier, after he says "A .45 caliber arrow", Aurora's dress keeps alternating between having straps and being strapless between shots. (00:13:25)
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: When Emma hears the scream and asks Ruby what's going on, her hands are bare, but as she runs off to investigate, she's suddenly wearing red gloves. In the next shot, her hands are bare again. (00:40:30)
Continuity mistake: When Regina is on the stretcher, she has a yellow coat around her shoulders. As she pushes Sidney away, the coat has vanished into thin air. (00:23:50)
Continuity mistake: When Emma and Hook kiss, in the shots from behind Hook, Emma tilts her head to the right. In the shot from behind Emma, she tilts her head to the left. In addition, Emma's left hand jumps from the back of his head to his shoulder between shots. (00:37:10)
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)
The Doctor - S2-E5
Continuity mistake: When Hook is tied to the tree, Emma raises her right hand to her mouth to whistle for the ogres. In the next shot, she uses her left hand. (00:26:45)
Continuity mistake: In Neverland, when Rumplestiltskin's father tells him to think of a food, a slice of cake appears in the palm of the boy's hand. When Rumple walks to place the cake down, suddenly there's a round, white doily under the slice, but when he sets the cake on the wood the doily is gone again. (00:16:50)
The Heart of the Truest Believer - S3-E1
Continuity mistake: When Neal and Mulan are walking to Rumpestiltskin's castle, after Mulan says "Your belief in love wasn't strong enough to overcome your fear of rejection", her hair keeps changing. In close-ups, some of her hair is over her shoulders; in the wideshots, all of her hair is behind her shoulders. (00:23:00)
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.