Barry's socks change color from beige to navy-blue sometimes.
In this and other early 1967-filmed episodes, the Sound Editor made the error of adding tropical jungle bird sounds to the background noise. By looking at the setting of the spaceship campsite and the giant foliage, he assumed it was a tropical rain forest and added background noises accordingly. This was corrected in later episodes, where there is no background noises with the exception of chirping crickets in night scenes.