Maybe he was just being mean or having a bad day and decided to do something hurtful.
Maybe she wasn't looking where she was going or there was something on the ground that caused her to lose her balance.
Maybe he was being clumsy or didn't see the person in front of him.
Maybe she was really angry with him for something he did.
Well, it could be that the girl was defending herself from a perceived threat. Or perhaps it was part of a crazy and unexpected plot twist in the cartoon's story.
It could be that the ground was uneven or there was something in his way that caused him to trip. Or perhaps he was in a hurry and wasn't being careful.
The cartoon kid might have tripped because he was distracted or there was an obstacle in his path that he didn't notice.
The reason might be that the girl has something the guy needs. Or maybe it's just a random act in a crazy cartoon world!
Maybe the guy has some bad personality traits or is influenced by bad surroundings.
Maybe he has a crush on her or finds her special in some way.
Maybe he likes her and wants to show his affection.