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: This is hard to see, but look at the whiskers on all the lions, the number of them changes about (I'm not exaggerating) 100 times, especially little Simba.
Continuity mistake: Scar's paw has a light brown line between the pad of his paw and his toes that disappears later in the movie.
Answer: Lions are not like humans, even though Disney tends to make them that way. It's rare for more than one or two full grown lions to be in a pride. Other males are in "bachelor prides" until they win a pride of their own. It's likely that Scar or Mufasa sired Nala.
Brenda Elzin