When Regina and Mary Margaret are talking at the school, Mary's fringe changes repeatedly between shots.
When Emma and August are crossing the road, a couple is crossing on the street perpendicular to theirs. When the shot changes, they are no longer there, and then you can see them begin to cross the road again.
When Regina looks at the note from Henry, there is a close up of the paper and it is clearly quite blank, and is supposed to be, revealing to us that she is making this up, as part of her plan. David, however, has no idea it is blank.
When August and Marco are talking, it appears to be evening and dark outside, except through the window in the back of Marco's shop where it appears to be daylight.
The boy who plays Pinocchio has brown eyes while Eion Bailey who plays him as an adult has blue eyes.