Sometimes, Sokka wishes people wouldn't think he's so stupid. Yes, he can be… strange at times (ditzy is a better word, but it's too girly for a warrior such as himself), but he's very smart. He's just got a natural curiosity.
But whenever he makes a plan for someone other than the Gaang, people scoff at him and say that they don't need his plans. And then they get killed.
Even the Water Tribe thinks he's dumb. When he came to visit his father, they hit him on his back – welcomed him – then laughed at him behind his back. They thought he wouldn't notice, but he did.
But Sokka was a genius. He could do math in his head quickly, he could play Pai Sho with the best of them, he could make brilliant battle plans, and he was an amateur detective.
Sure, he preferred using an abacus because the word "abacus" made him laugh. Sure, he chose not to play Pai Sho because it was slow and bored him. Sure, some of his plans failed. Sure, the pipe made him look goofy while he was solving cases, but the bubbles reminded him of water and that reminded him of home.
But then at times, when he's being underestimated by some other Fire Nation soldier or even by the Fire Nation princess (the one that reminded him that not all princesses are the same, because Princess Yue would never have acted like that), he likes when people think he's stupid. Because if everyone knew that he was so smart, it would be so much harder to get away.
And he always likes the looks on their faces when they realize that Sokka – the moron – has outsmarted them.