We Are Both - S2-E2
Revealing mistake: When Regina is trying to escape on horseback, as she says "Come on, Rocinante, go!", you can see that the one who's actually riding the horse is Lana Parrilla's stunt double. The stunt double's face can also be glimpsed when Regina is caught by the tree branches, and when she drops to the ground. (00:05:20)
We Are Both - S2-E2
Revealing mistake: When Mary Margaret tries to escape and Mulan uses a sling to bring her down, you can see that the one who falls to the ground is Ginnifer Goodwin's stunt double. (00:39:50)
Revealing mistake: As Killian Jones and Rumplestiltskin duel, there is an overhead shot of them fighting, and in the next shot, you can see that Robert Carlyle and Colin O'Donoghue have been replaced by their stunt doubles. (00:17:35)
Revealing mistake: When Killian Jones is dueling Rumplestiltskin and is pushed into some barrels, you can see that the one who actually falls down is not Colin O'Donoghue, but his stunt double. (00:18:20)
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)
Tallahassee - S2-E6
Revealing mistake: When Neal is being chased by August, he runs on top of a car before attempting to jump the fence. Just before he jumps on top of the car, you can see that the one who actually performs this action is Michael Raymond James' stunt double. (00:26:40)
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)
Revealing mistake: When Hook attacks Mr. Gold, if you watch as he pushes Emma out of the way, you can easily see that one who actually pushes Jennifer Morrison is Colin O'Donoghue's stunt double. When Hook pushes Mr. Gold against the security gate, it is the stunt double who pushes Robert Carlyle. (00:18:25)
Welcome to Storybrooke - S2-E17
Revealing mistake: After Regina burns the curse that will make Henry think he loves her, when Henry walks over to Emma and the others a few shots later, Regina has the curse scroll in her hand again. (00:36:40)
Selfless, Brave and True - S2-E18
Revealing mistake: As Tamara opens the envelope of cash in the bar in Hong Kong, the words "motion picture use only" are printed on the dollar bills. (00:18:30)
Revealing mistake: When Hook is down in the pit, trying to escape the undead Maleficent, after he says, "Maleficent. Love you in earth tones", there is a wide shot of Hook and Maleficent where you can see the face of Colin O'Donoghue's stunt double. The stunt double's face can also be seen in the shot where Hook stands up after climbing on top of the rock. (00:22:20)
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.