Seventeen-year-old Sodapop is Mr. Personality, and he backs that up with lots of heart. Like his brother Darrel, he's fashion-plate handsome, and since he's a Curtis, he's smart, athletic, and hardworking to boot. In contrast to Ponyboy's conflicted emotions regarding Darry, Pony's feelings for Soda are entirely positive. He idolizes and loves his older brother and sees how smart he is.
Pony's only problem with Soda is that Soda dropped out of high school. He dropped out because he wasn't excelling in school, and because he needs to work to help support the family. But, for Pony, this is still a source of shame, and probably guilt as well. On a conscious or subconscious level, Pony feels that if Soda didn't have to help provide for him, his brother might still be in school. His shame is also due to the social stigma of dropping out of high school:
"Dropout" made me think of some poor dumb-looking hoodlum wandering the streets breaking out lights – it didn't fit my happy-go-lucky brother at all. (2.39)
Pony later learns that, although Soda doesn't want Pony to drop out of high school, he's happy with his own choice to do so. He likes his work at the gas station, and says he wasn't getting anything out of school. What do you think? Should Soda have fought to get an education no matter what? Is it okay for some people to leave high school, or should everybody graduate?
In any case, Soda is always cheery, in sharp contrast to brooding and moody Pony and Darry. He takes his role as middle brother seriously, and is constantly the in-between for Pony and Darry, acting as a buffer against their constant clashes. As with Darry, Pony hasn't been seeing the whole picture.
Since Soda's so cheery and funny about the whole thing, we might get the impression that he's an uncomplicated guy, who enjoys playing peacemaker and isn't really affected by the tension. Both brothers have been taking him for granted, in part because they're too wrapped up in their own dramas, and in part because Soda waits a long time to tell them how he really feels.
Only at the very end of the novel do Soda's layers start to emerge. We learn lots of important things that deepen his complexity as a character. First, we learn that his brothers' fighting is really hard on Soda.
"It's just… I can't stand to hear y'all fight… Sometimes I have to get out or… It's like a middleman in a tug o' war and I'm being split in half… We're all we've got left. We ought to be able to stick together against anything. If we don't have each other, we don't have anything." (12.51)
This also lets us know that Soda's role as peacemaker isn't just superficial, but is related to his core values and his way of looking at family. We see just how much he values peace and his brothers.
We also learn that Soda has been having hard times with his girlfriend Sandy. Pony had no idea. He knew Soda was in love with Sandy and planned to marry her, but Pony sure didn't know she was pregnant with another guy's child. (Ouch.) He also had no idea that Sandy had left town to raise the baby, even though Soda wanted to marry her and raise the child as his own. See Sandy's section for some more discussion of this, but here we want to talk about what this says about Soda.
Namely, we think it speaks well of him. He loves Sandy completely, and can look past the fact that she cheated on him. He's willing to breach social conventions and be a father to a child that isn't his, taking on even more responsibility. But all that goodness comes to nothing. It's pretty clear that Sandy's parents rejected Soda as son-in-law material. Luckily, Soda has lots of ladies vying for his attention and will probably fall in love again soon. Or, who knows—maybe there's still a chance for him to be with Sandy.