It could be that he had a fight with his friends. Or perhaps he was scolded by his parents and that made him angry.
Maybe he didn't get the toy he wanted.
Maybe he didn't get what he wanted. That could easily make a boy in a cartoon angry.
The cartoon boy could be angry because his favorite snack was out of stock. Or it could be that someone broke his favorite toy. Maybe he was scolded by his parents for something he didn't think was his fault.
Maybe he didn't get what he wanted or someone was mean to him.
It could be that someone was mean to him and that made him angry. Or perhaps he lost a game and was disappointed.
Maybe he's had a bad day or someone upset him.
Well, there are many reasons. Maybe he lost a competition he really cared about. Or perhaps his best friend let him down. Another possibility is that he's dealing with a big problem at school that makes him feel this way.
Maybe it's because his expressions and actions are really funny and relatable.
It could be that the parents were too strict or didn't give him the freedom he wanted. Or perhaps they made a decision that the boy didn't like.
Maybe he didn't get what he wanted or someone made him upset.