Well, there are many. For example, in some adventure cartoons, the brave protagonist might have yellow hair.
There could be various cartoons. Maybe in a fantasy one, a magical yellow-haired boy could be the key character. Or in a comedy, a funny yellow-haired boy brings the laughs.
It depends. In some action cartoons, a yellow-haired boy could be a powerful fighter. Or in a slice-of-life cartoon, a yellow-haired boy could be a regular kid with interesting stories.
He might be a lively and adventurous type. Maybe he's always ready for new challenges and has a lot of energy.
Maybe it's a school-themed cartoon and the orange-haired boy is the mischievous but smart student.
It could be a magical girl genre cartoon like 'Cardcaptor Sakura' where there might be supporting male characters with long hair. Or it could be an adventure cartoon where a long-haired boy is the hero, like in some versions of 'One Piece'.
It could be an adventure story where they go on exciting quests together.
He could be fun-loving and energetic, always ready for adventures.
It could be a fantasy cartoon where the boy has magical powers and yellow hair to signify his special abilities.
You could look at 'Soul Eater'. The character Soul Eater Evans has red hair and is a significant protagonist. There are likely many others too, depending on your specific preferences in animation style and story.
Maybe it's a fantasy cartoon where the fat boy with yellow hair has special powers or goes on magical quests. There could be all kinds of imaginative elements involved.
It could be a fantasy-themed cartoon where unique character designs are common. Maybe the boy has magical powers or is from a strange world.
It could be a school-themed cartoon where the boy is a smart student with glasses and brown hair.