Continuity mistake: When Emma arrives in town, two Storybrooke businesses, Standard Clocks and its neighbour, Modern Fashions, can be seen in a shot though a window. In the shot from above where Emma's car slows down, the name on Standard Clocks is Kaido (a real-life business in Steveston, the Canadian town which doubles as the town of Storybrooke), and there is now a white sign on Modern Fashions, which wasn't there in the first shot. (00:15:45)
Continuity mistake: At the end of the episode, the hands on the clock tower move forward for the first time. In the wide shots, the circle surrounding the clock, as well as the wooden beams forming the outer edges of the area around the clock face, are white. In the close-up where the minute hand moves, the circle and edges are brown. Also, in the wide shots, the area around the clock face of the building is shaped like a square, but in the close-up, it is in the shape of a trapezoid. The same thing happens when the clock moves in "The Thing You Love Most", "A Land Without Magic" and "Darkness on the Edge of Town." (00:41:25)
Continuity mistake: Emma Swan has a flower tattoo on her left wrist. It can be glimpsed during her date with Ryan, and is visible when she's sitting at the table with Mary Margaret in "The Thing You Love Most", and when she's on the phone with Ruby in "Red-Handed." However, when she opens the door for Henry in "Pilot", the tattoo is gone. The same thing happens when she unlocks the door to her room at the inn in "The Thing You Love Most" (in the scene where she is evicted), and when she's pressing a pack of ice against her wound in "The Heart is a Lonely Hunter."
Continuity mistake: When Emma arrives at the restaurant, as the elevator opens, a waiter walks past. In the next shot, the waiter walks past the elevator again. (00:04:55)
Continuity mistake: When Emma meets up with Ryan at the restaurant, as he says, "Well, it is the Internet", Ryan is positioned next to Emma and moves to walk around her. In the next shot, he is already standing behind her as he pulls out Emma's chair. (00:05:15)
Continuity mistake: When Emma is driving through downtown Storybrooke, in some shots, the real-life businesses in Steveston Village (the Canadian town which doubles as the town of Storybrooke on Once Upon a Time) have not yet been transformed into Storybrooke businesses. For example, a sign on a building on the left side of the road (in the first shot) says Pacific Net and Twine, and on the other side of the street (in the shot where Henry is heard saying, "Forty-four, not-telling-you street"), the name on the local bakery, which is Romania Country Bread, and is sitting next to two businesses called Kaido and Splash. In "The Thing You Love Most", the buildings have been transformed into the Storybrooke businesses seen throughout the rest of the series: For example, Pacific Net and Twine has become Atlantic Twine and Net, the bakery has been renamed Storybrooke Country Bread, and Kaido and Splash have become Standard Clocks and Neighbor's, respectively. Also, in "The Heart is a Lonely Hunter", when Graham first meets the wolf, as the wolf walks away from him, in the background, the name "Pacific Twine and Net" appears on a window pane. (00:15:40)
Continuity mistake: In the scene where Snow is in Emma's nursery room, trying to convince Charming to talk to Rumplestiltskin, the shots have been flipped. The easiest way to spot this is Charming's scar, which is on the wrong side of his face. (00:10:30)
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 Henry and Emma arrive at Storybrooke and Archie Hopper comes over, Archie's scarf alternates between both ends hanging down his shoulders, and one end lying on top of his shoulder/neck. (00:15:55)
Continuity mistake: When Henry is in Emma's apartment, the amount of juice in the bottle repeatedly goes up and down between shots. (00:08:40)
Continuity mistake: When Regina casts aside the guards at Snow White's wedding, one of the guards drops his sword on the floor. In the following overhead shots, the sword has vanished. This is best seen when she turns around after saying "I shall destroy your happiness, even if it's the last thing I do." (00:02:45)
Continuity mistake: When The Evil Queen crashes Snow White's wedding, the guests alternate between looking at the queen and averting their gaze between shots. (00:02:30)
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.