Audio problem: (May only apply to the original VHS release.) When Scar has Zazu locked up in a cage, Zazu mentions Mufasa's name and Scar yells at him, "What did you say?" Right before Scar's actual line, whilst Zazu is talking, you hear Scar's "What did you say?" line very faintly in the background, even though Zazu has not even mentioned Mufasa yet.
Continuity mistake: The whites of Simba's eyes change frequently through the movie, from yellow to white. They're yellow up until the scene where Pumbaa, Timon, and Simba are stargazing; after that they change back and forth frequently. During the Mufasa-in-the-sky scene, when Simba asks, "How can I go back? I'm not who I used to be," they change from yellow to white and back within three frames.
Deliberate mistake: At the elephant graveyard, little Simba claws Shenzi in the face. When Mufasa saves Simba from the hyenas, the cuts are gone, a few seconds later. [This was done intentionally, I'm sure, for two reasons. The first being, Disney doesn't let fresh scars linger on the screen too long. Secondly, during that same scene when Mufasa rescues Simba & Nala, he claws Banzai in the rear. To stress the point later in the movie, that severe scar is shown too, but only briefly, it too disappears because of reason 1. Still a "mistake", but there's why.] (00:21:50)
Continuity mistake: When Timon rides Pumbaa through the vultures that are crowding around Simba, they run right over where Simba should be, but he's not there. 2 seconds later, after all the vultures are gone, Simba is back. (00:42:05)
Continuity mistake: At the beginning when Rafiki puts the paint on the picture of Simba (on the tree trunk) the paint goes on a different color than it is. The film makers admit this mistake on the commentary. (00:07:00)
Continuity mistake: During the stampede in the gorge, when Simba jumps up on the dead branch, he leaves very distinct claw scratches. Then in the following scenes they're gone, although other marks and details on the branch remain. (00:34:10)
Factual error: When Mufasa is showing Simba the kingdom from Pride Rock they are facing the sun, yet Pride Rock's shadow is visible below them. Also in the same position, you see that they have shadows behind them. Then a few seconds later when Simba sees the shadow area the shadows are in front of them while you can see part of the sun to their left side. They would be facing south when the sun is east. How are their shadows in front of them?
Continuity mistake: When Rafiki is showing Simba where his father is, Simba is following Rafiki through the trees and they arrive at a river/lake. Rafiki says 'shh' and pulls the grass apart. In the shot facing him and Simba, Rafiki is only holding the grass on the left back, but the grass on the right is bent back the exact same way, without anyone holding it back.
Continuity mistake: When Simba and Nala fall through the dead elephant, there are some small rocks near them. But after the hyenas say, "Here kitty kitty kitty," Simba makes a small roar and the rocks are gone.
Deliberate mistake: Rafiki is supposed to be a mandrill, but mandrills do not have tails. In the extended version DVD, there is a commentary by an animator who specifically admits that he knew that mandrills don't have tails (at least not like the length that Rafiki sports throughout the movie), but he put one on him anyway to make him more monkey-like. (00:02:40)
Continuity mistake: When Simba walks away from the jungle and Timon says "He looks blue," Simba is at a fair distance from the shadow of the tree. But a few shots later, Pumbaa comes to Simba and asks, "Kid, what's eating ya?" but Simba is now closer to the shadow of the tree.
Factual error: When Simba and Nala meet as adults, they rub heads and begin to purr. Lions can purr, but they only purr when they exhale, and Simba and Nala were purring when inhaling and exhaling, like house cats. (00:58:15)
Continuity mistake: When Timon and Pumbaa are inspecting unconscious Simba, Simba's paw is lying over his eye. In the next shot, right before Timon lifts the paw up, it has moved to below his eye.
Continuity mistake: When Simba and Nala are in the elephant graveyard, Simba goes to see if "it's brains are still in there" and he's past the base of the trunk. But when Zazu pops up in front of him, he hasn't passed the base of the tusk yet.
Continuity mistake: When Rafiki dips his fingers in the orange paint to put a mane on Simba's picture, the paint is not on his thumb. He raises his hand up close to the picture, then, a split second later in the next shot, the paint is on his thumb with which he starts to paint the mane. He did not have time to dip his hand in again.
Continuity mistake: After Pumbaa kisses Simba's feet, Timon says, "Don't he's not the king," he puts his hands on the middle of Pumbaa's snout. But in the very next shot, Timon's hands are now at the top of Pumbaa's snout.