What Happened to Frederick - S1-E13
Revealing mistake: When Regina finds Henry with Emma at his playground In "Fruit of the Poisonous Tree", her license plate number is 40F5 TH. When the gym teacher finds Kathryn's car in this episode, his car has the same license plate, indicating that it is a reused prop. The same license plate appears on yet another car when August drives off with his motorcycle in "The Return", on Archie Hopper's car when he tries to cross the town line in "We Are Both", and on a parked car when Emma and the others arrive in Storybrooke in "Mother." (00:40:10)
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)
Other mistake: In "The Heart of the Truest Believer", Rumplestiltskin has his shadow removed from his body, and therefore should not cast a shadow. But in Neverland, his character frequently casts a shadow, especially in scenes with campfires.
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)
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)
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)
Continuity mistake: Regina and Daniel are in the stable. Regina's hands are on his face, he reaches up and pulls them down, cut to behind Daniel and her hands are back up on the side of his head. Cut back to side view, and Daniel's hands are still holding Regina's down. (00:16:40)
Continuity mistake: Belle is talking to Rumplestiltskin and sitting on his dining room table. The red rose in the vase he gave her keeps moving. It is leaning to the right, to straight up, then to leaning to the right again. Neither of them touch it, so it should not be shifting around.
New York City Serenade - S3-E12
Plot hole: When talking to Hook about the photos, Emma states he could have photoshopped them to make it look like she and Henry were in Storybrooke, however she had taken them directly from Henry's camera and had them developed. So Hook had no way to photoshop the pictures from inside the camera. (00:27:00)
Continuity mistake: When Mary Margaret gets thrown by the Lily dragon into a rock, her blood smear on her head is large and messy. They cut away and cut back to her quickly and it is nice and neat with two blood drop lines slowly forming away from the cut. (00:44:00)
Revealing mistake: When Snow White and Prince Charming hurriedly make their way through the woods in the beginning of the episode, in the shot where Snow White jumps over a log, you can see the face of Ginnifer Goodwin's and Josh Dallas' stunt doubles. Josh Dallas' stunt double can also be seen as Snow and Charming are running thought the woods in the previous shot.
Tallahassee - S2-E6
Revealing mistake: When Hook and Emma are climbing up the beanstalk, as Hook remarks, "First beanstalk?", you can see that Colin O'Donoghue is actually gripping the vine with his left hand, which is covered up by his sleeve; the hand that was cut off. (00:08:50)
Snow Drifts - S3-E21
Continuity mistake: Aboard The Jolly Roger, when Emma is keeping past Hook occupied while future Hook skulks around the room, in a wide shot, future Hook sneaks past a corner. In the next shot, he begins to sneak past the very same corner again.
Chosen answer: Even if one can see the future, it can be somewhat vague and left open to interpretation.
raywest ★
He can sees the future all jumbled up. It is like a puzzle, it is hard to put together, but even when he does put it together it is not set in stone the future can change.