In many of the interior close-up shots, the actors' own teeth are visible behind the teeth of their ape masks.
In the pilot episode (after the astronauts have been captured by Urko), Alan abrades the ropes binding his wrists against a rock. Yet in the close-up of his wrists, the ropes are not frayed where he had been rubbing them and they don't break. They just fall off his arms.
It is clear from the numerous shots of the palms of Galen's hands that they are gloves, though the character doesn't wear gloves.
During the closing credits of each episode was a statement "Based on characters from Planet of the Apes (1968)". This is not quite true, as there are no characters from the original novel or movie that appear on this series; only two character names. Galen was a doctor (named Dr. Galen) who assisted Zira as more or less a trained vet on the original film. The Galen on this series was an underling of the Ape Council. Zaius on the original film (Dr. Zaius) was head of the Ministry of Science and Keeper of the Faith. Zaius on this series was merely a politician (not titled "Doctor"), head of the Ape Council.