Revealing mistake: After the scene with Emma and Henry at the playground, there is a wide shot of Storybrooke Main Street. As the camera pans down, in the upper right hand corner, you can see the clock tower, but without the top two stories (the top two layers of the clock tower, including the clock, are CGI). (00:06:15)
Revealing mistake: In the very first shot of Emma and August on the motorcycle, you can see the faces of Jennifer Morrison's and Eion Bailey's stunt doubles. (00:20:25)
Revealing mistake: When Sheriff Graham pulls in front of Emma in a police car, the big sign on the storefront behind Emma says "Storybrooke Coffee Co." However, as Graham gets out of the car, you can see a circular sign on the side of the building, which says "Steveston Coffee Co"; Steveston is the Canadian town which doubles as the backdrop for the town of Storybrooke on Once Upon a Time. (00:05:30)
The Thing You Love Most - S1-E2
Revealing mistake: When Emma is reading the Storybrooke Daily Mirror in Granny's Diner, the article on the front page is just the same block of text repeated three times. (00:12:10)
The Heart is a Lonely Hunter - S1-E7
Revealing mistake: When Emma and Graham are chasing after the wolf into the graveyard, there is a shot where the wolf turns its head toward them, closes its mouth and perks up its ears, while growling. The wolf howls, before turning its head toward them again, and you can see that it is exactly the same shot that was used earlier, only this time, the wolf can be heard whimpering. (00:28:40)
The Thing You Love Most - S1-E2
Revealing mistake: When Emma walks Henry to school, as Emma says "Because I'm the daughter of Snow White and Prince Charming?", a reflection of the clock tower building is visible in the window behind her, only there's no clock (the top two layers of the clock tower, including the clock, are visual effects). (00:13:40)
Revealing mistake: When Graham offers Emma the job as deputy sheriff, as he says, "Why don't you think about it", in the background, the name "Steveston" appears on the sign on a business next to Kisamos Greek Taverna. Steveston is the name of the Canadian town which doubles as the town of Storybrooke for exterior scenes. (00:05:50)
Revealing mistake: When Emma leaves the apartment to go looking for Ashley, she and Henry walk down the streets of Storybrooke, toward Emma's car. As Emma says, "Because I know", in the background, you can see a business called Steveston WineMakers. Steveston is the name of the Canadian town which doubles as the town of Storybrooke on Once Upon a Time. (00:14:35)
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)
Revealing mistake: When the newly hatched dwarves are being cleaned, there is a shot where Sleepy is seen from behind as he's drying himself with a towel after getting out of the bath tub, and you can see that the actor is wearing black shorts underneath. (00:09:45)
Revealing mistake: As Moe French steps out of his florist's van, he is greeted by Mr. Gold and his lackey. As. Gold says, "Well, this is just perfect", in the background, you can see the clock tower building, but without the clock tower (the actual clock tower is CGI). (00:03:50)
Revealing mistake: As Mr. Gold bangs his head on the table after being spritzed with pepper spray, you can see that one performing this action is Robert Carlyle's stunt double, and that the stuntman merely hits the table with his hands. (00:10:20)
What Happened to Frederick - S1-E13
Revealing mistake: At Granny's, when Emma and August ride off on the motorcycle, you can see that the one driving is actually Eion Bailey's stunt double. (00:21:45)
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)
Revealing mistake: When Rumplestiltskin is screaming at Snow and Charming about their unborn child's name, he speeds up for a few seconds and looks comically fast forwarded.
Revealing mistake: At the end of the episode, when Emma goes to Gold to ask for his help, we can see he's wearing a wedding ring on his left hand in addition to the usual ring with the light blue stone he wears on the right. That's actually Robert Carlyle's own wedding ring; as he wrote during a twitter Q&A session, he forgot to take it off before they started to film. (00:40:35)
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.