MUFASA: That "hairball" is my son. And your future king.
When Scar insults the newborn Simba by calling him a hairball, Mufasa is there to defend his young son and put Scar in his place.
ZAZU: There's one in every family, sire.
Zazu's assurance echoes a timeworn truism: every family has its black sheep. Or scarred lion. Or general pain in the butt.
MUFASA: That's 'cause nobody messes with your dad.
Mufasa takes his role as father very seriously and is always eager to remind Simba—who, in this instance, was almost just eaten by hyenas—that he's always going to be there for him.
MUFASA: Simba, let me tell you something that my father told me.
This quote echoes the Circle of Life motif we discussed earlier: families grow, roles change, but events will always repeat themselves. In this case, Mufasa once received some loving wisdom from his own father and now feels the need to pass it down to his son.
MUFASA: Whenever you feel alone, remember that those kings will always be there to guide you. And, so will I.
Mufasa explains to Simba that the kings of past generations—i.e., Simba's great-great grandfathers—are chilling up in the stars, watching over him. Mufasa is giving his son a sense of family with a downright cosmic perspective, a perspective that Simba will make use of when he seeks guidance from his father's ghost after fleeing the Pride Lands.
SCAR: Lucky Daddy was there to save you, eh?
In his typical malevolent fashion, Scar is mocking the close bond Mufasa has with Simba. This marks Scar as a family member who is utterly disrespectful of all things familial.
SIMBA: Well, somebody once told me the great kings of the past are up there, watching over us.
Simba says this to Timon and Pumbaa one night as the trio looks up at the sky. Although he doesn't want to reveal that that "somebody" was his father because the memory is far too painful, it's clear that what Mufasa said impacted his young son greatly.
NALA: Wait till everybody finds out that you've been here all this time! And your mother—what will she think?
Nala is shocked that Simba abandoned his family but eager to get him back home to them. Like Mufasa, Nala has a strong sense of loyalty to family.
GHOST MUFASA: Simba, you've forgotten me. You've forgotten who you are … you are my son and the one true king.
These are the words Mufasa speaks to Simba from beyond the grave. He's not so much urging Simba to return to the throne as he is asking him to remember how important his family is. Which, of course, results in Simba returning to the throne.
SCAR: But, Simba, you wouldn't kill your own uncle.
Very telling that the only time Scar really cares about family values is when his life is in danger.