Simba, at first, seems to have grown up into quite the irresponible King. But soon (with some help and head whacking) we see that there IS a thinking, responisble adult inside that young exterior.
He also has developed the courage to stand up to his totalitarian-ruler Uncle Scar along with the nesiccary fighting skills. With some help (again) he overthrows his uncle and takes his place as King. The last we see of him is a Mufasa-Serabi-Baby Simba-type stance on pride rock with the futer in Rafiki's hands.
