Deliberate mistake: After Baloo and Bagheera escape from the monkeys, they both have a black eye. However, during their conversation by the water, between shots their black eyes vanish. [This is a Disney tradition, but still a mistake.]
Deliberate mistake: When 11 is dropped into the water and eaten by the piranhas, although the ravenous fish probably ate most of her and what was on her, there should at least be pieces of clothing that would rise to the surface in the flurry of activity. Not to mention that even though the water is a murky green all the blood from her body should have created a temporary, but very noticeable darkening of the water.
Deliberate mistake: When we look toward the bar, Mrs. Robinson's calf is well below the edge of the bar. In the next classic shot of Benjamin filmed from behind the bar through Mrs. Robinson's bent leg, her calf is above the bar. (00:12:30)