I'm in the process of giving all of the children/teens from Sunset Valley a collective makeover, but here are two to start. Both have been aged up to YA.
Malcolm Landgraab, left to story progression, tends to age up with a rather...
homely appearance. It wasn't until I brought him into the household in my first story project that I realized just how good looking he actually was, so long as you dress him up right.
I got rid of the ponytail that he usually ages up with and gave his glasses back, then had him hit the treadmill. His facial structure does not take well to being super-thin, so I kept him at a slightly above-average weight. The outfit is well put together (he's definitely not the t-shirt type) but a bit more comfortable than your standard dress shirt and tie. That sweater from University just seems to fit him.
I took a simple approach to Mortimer Goth.
In all reality his appearance didn't need a lot of work. I didn't touch his muscle tone or weight at all.
That
hair...I haven't seen a sim yet that doesn't benefit from that hairstyle, and Mortimer is just
gorgeous with it. The facial hair is an homage to his father. Briefly I toyed with the idea of putting him in more formal-ish attire, but Morty doesn't strike me as being too pretentious, so casual seemed to fit him better.