Continuity mistake: In the opening scene, three people suddenly appear at the bottom of the screen, in the middle of the road.
Suggested correction: This is too vague. The opening scene is (what appears to be) a single tracking shot that moves along several different roads. At no point did I see any characters suddenly appearing at the bottom of the screen in the middle of the road. Even the characters that were digitally inserted into the far background when "London, 1888" appears onscreen are there the entire time the shot is on them.