Why did Scar look thinner and older than Mufasa?

[DragonFromNewYork]

I believe the reason for Scar's design was solely for a "villainous" appearance. I was watching a "Making of" for TLK a while back, and there is an entire segment devoted to the design of Scar. If I remember correctly nearly all the animators said that they intended on giving Scar a more humanesque appearance compared to the other lions (which I do believe he does). I don't necessarily think that he looks older than Mufasa, it' just that his features are so different than his brother's that his aging is different.
Also, Scar is thinner simply because it is a stated fact that he is the weaker brother. Although he is surely stronger than he looks (he sends Sarabi flying with one hit), he does not require the "brute strength" that it would take to even think of challenging his brother.

It still is pretty interesting, though, to see how much Scar changed from the original concepts.
In "King of the Jungle" Scar is GIGANTIC-

-and I wonder what it would be like if Scar remained more like his original concept (having one eye missing, being afraid of lightning, larger, more unintelligent, etc.)

[ScarLoyal]

Maybe Scar and Mufasa were half-brothers? Mufasa's mother probably would of been more 'chunky' and 'Queenly' but Scar's mother would of been more 'scrawny' and 'cold'.