Why do some characters in Riman narrow their pupils when they are surprised or afraid?

This is just an exaggerated expression. People's pupils will shrink in an emergency, but it is not obvious. The expressions of cartoon characters can be expressed at will, with their pupils narrowed, their mouths wide open and even their eyes straight. These look normal.

In many cartoons, exaggerated expression is very necessary, because cartoon characters are too peaceful, which makes cartoons look lifeless or interesting. Why do many people like Cherry Maruko and Crayon Shinchan? There are not many highlights in the plot, and there are only a few characters in each episode. This cartoon is really overdeveloped, except for the "jokes" that make people laugh, and even many adults are watching it.

The world of animation itself is full of all kinds of whimsy. There won't be much market for mediocre themes. Fierce fighting can be compared with the sky, and the exaggerated expression is like a child entering a haunted house. These are just a technique in animation description. After all, almost everything is fiction, and it is normal for pupils to contract when they are surprised or afraid, because there are more exaggerated plots or expressions than these.

Finally, any exaggerated depiction should follow basic common sense. Why do pupils shrink when you are afraid and surprised? This is also the most basic common sense, because people actually shrink when they are afraid, but it is not obvious, and animation can be expressed at will, so the gap between the two is obvious.