I think it's to catch people's attention. Funny cartoon kids with muscles are something different and can make the cartoon more engaging and visually interesting.
It could be that the kid saw someone else do it and is imitating them. Or perhaps the kid is pretending to be a strong superhero.
Because kids' innocence and playfulness can be exaggerated and presented in a humorous way through cartoons.
They're often drawn exaggerated for effect, making the animals look stronger and more powerful.
You might see characters like buff lions or strong gorillas in some cartoons. These animals are often shown with well-defined muscles to give them a powerful look.
I think it could be a creative choice by the artist to stand out or convey a certain mood or theme.
Cartoon kids might develop muscles through intense physical activities or training in their fictional worlds.
It could be the exaggerated expressions or the way the muscles are shown in a comical way.
It could be for a humorous or exaggerated effect. Cartoons often use such unusual depictions to catch the audience's attention and make them laugh.
Maybe it's just for a comical effect to make kids look more charming and interesting.
The muscles of the cartoon guy in high school are typically drawn based on the style and genre of the cartoon. They could be drawn with sharp lines and bold shading to stand out, or presented in a more subtle way to match the overall aesthetic of the show.