A scared guy in a cartoon could have things like sweating a lot, having his heart pounding shown visually, or maybe even having cartoonish thought bubbles with images of what's scaring him. The way he moves might be all jittery and uncoordinated too.
A scared guy in a cartoon might have wide eyes, a pale face, and maybe be shaking or hiding.
Maybe he saw something really creepy or got into a dangerous situation.
Maybe there's a creepy monster in it that scared him.
Maybe he saw something terrifying. That could be the reason for his scared reaction and jumping.
Maybe he has had bad experiences related to it or has a strong sense of justice against sexism in cartoons.
Perhaps the cartoon guy is scared and running because he just had a close encounter with danger. It could be a natural disaster, a wild animal, or even a magic spell gone wrong. These kinds of scenarios are common in cartoons to keep viewers engaged.
It could be that he's imagining something scary or has a fear of the dark. Sometimes our minds play tricks on us when we're in bed!
Perhaps he has a phobia and something triggered it. Like if he's afraid of heights and suddenly finds himself on a tall cliff.
He might be scared because he's in a strange and unfamiliar place. Or perhaps someone threatened him.
It could be that he's in a situation he's never been in before and it's freaking him out. Or perhaps he just has a really vivid imagination and is imagining something terrifying.
Perhaps they're at a school that's rumored to be haunted and they have to spend the night there. The tension builds as they experience strange noises and sights. How they overcome their terror and solve the mystery could be the focus of the story.