Revealing mistake: After Mark gives his father the keys and tells him to park the van, in a following shot when Elizabeth joins the gurney rush with Carter, as she's walking backwards there's a distinctive large bulge at the back of her waist from the mic transmitter. (00:10:55)
Revealing mistake: Near the beginning of the show, Mark's father puts a bulb into an old slide projector. Then there is a small explosion with smoke and flames - watched carefully, we can see are actually coming from the other side of the projector - the flames can be seen shooting parallel and close to the floor, which wouldn't have happened if the explosion actually came from the projector.
Answer: It was in "Chaos Theory" which is the first episode of season 9 (time code 00:13:55).
Super Grover ★