Maybe he's trying to prove himself or just having fun. Kids do all sorts of things for different reasons.
The weak little kid might be throwing the baseball to build strength or to show that he's not as weak as he seems. Maybe it's a way for him to make friends or fit in.
The reason might be that he has a passion for baseball and wants to improve his throwing technique. Or maybe it's a dare or a challenge from someone.
The wimpy kid might be throwing a baseball as part of a challenge or to show off to his friends. It could also be related to a sports event or practice.
Maybe the kid is having a bad day and is taking out his frustration by throwing the baseball roughly.
The kid might have a determined look on his face, with his arm swung back ready to throw the ball with all his strength.
It could be that the kid is not focused or is too nervous, which affects the way they throw the baseball in the cartoon. Also, the animation might not be very well done, making the throw seem worse than it is.
There could be several reasons. Maybe he's got poor muscle development, or he hasn't been taught the correct way to throw. Or it could be that he's too nervous and that's affecting his performance.
The cartoon boy might be throwing the baseball because he's part of a team and it's his turn to pitch. Or he could be practicing on his own to improve his aim and strength.
It could be a cartoon where the boy is in a local baseball tournament and his throwing skills are the key to his team's success. The cartoon might focus on his determination and hard work to perfect his throws.
Maybe the kid is just having fun or being a bit naughty.
It could be that the kid has a stomach bug or got overexcited and it triggered the vomiting. Or perhaps they were exposed to something that upset their stomach.