Audio problem: When Mr. Wonka bites into a teacup at the end of the song of the room with the Chocolate River, you hear a crunching sound, yet it looks like he has to "tear" the cup a bit. How can he crunch on somethng that requires him to tear at it? [In an interview, Gene Wilder stated the cup was made out of wax - not excusing the mistake, but in case anyone was wondering...]
Continuity mistake: When Charlie is working with Mr. Turpentine on the wart-removing potion, the bottles and cups on the table change between shots.
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.