Revealing mistake: When Mrs. Teevee puts the shrunken Mike into her purse, it is a very obvious fake Mike.
Continuity mistake: When the first "good egg" falls on the eggdacator, its position changes between shots.
Continuity mistake: When Charlie sees the newspaper about how the fifth ticket was faked, the position of the newspaper in the man's hands changes between shots.
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.
Visible crew/equipment: There is a cameraman shooting near the gate of Wonka's factory: he is strategically placed to get up close shots shown in the movie yet he blends in to the crowd to make the movie audience think he is one of the many media technicians filming the event of Wonka opening his factory. Later, when the guests are passing through the gate, the cameraman has disappeared.
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.