In the scene where the doctor injects Zira with a needle to calm her down, and she begins telling the true story of their planet, watch her mouth as she speaks. You can clearly see the lips and teeth of actress Kim Hunter inside the ape mask. I know it was 1973 but come on, you would think they would have fixed that for the DVD release.
And how would you suggest they fix this and still keep the movie original? Even though it was 1973, the make-up techniques used were cutting edge and state of the art in those years.