It would be impossible to channel gas into the subway system without it escaping into the air above ground.
At about 1:12:40 into the movie, when the child is trying to open the door, shadows of hands can be seen directing the child.
When A.J. 'The Reverend' Shepherd is locked in the sewer by that mysterious stranger, a crew member can be seen in his glasses.
When Lauren is in the shower, a blue strapless top is visible. (Open Matte Framed Version Only)
As they are leaving Central Park, Lauren speaks "He wouldn't" over Murphy's "Of course not", then starts again: "He wouldn't" etc..