Other mistake: During the glass elevator ride, first Joe points out their house can be seen but then when the area is shown on camera, no little house like theirs is in the shot. Next, Charlie says he sees his school, and again when the shot looks down below, no school at all is seen, but rather just streets that come together through a small tunnel and random houses.
Visible crew/equipment: When everybody first comes in the main room with the chocolate river, there is a shot of all of them standing in the doorway. At the bottom of the scene is the shadow of the camera.
Visible crew/equipment: In the Fizzy Lifting Drink scene, as Wonka leaves the room, a bubble machine is just visible at the bottom left of the screen.
Chosen answer: In the original book, Charlie has an obsession with chocolate that he only satiates once a year on his birthday. Also, at this point in the book, the Bucket family is going through an extremely hard time and Charlie has had less food than he usually would have, so he is EXTREMELY hungry.