The little visual tropes used in different styles of animation to depict certain things without really trying. For example, in anime, the bead of sweat, the pulsing temple, or the red line over the cheeks and nose to denote blushing.
Instant anger! Instant worry!
Western animation totally has these too, but for some reason I don't notice them and they don't distract me, probably because I was raised with Western animation and am used to those shorthands. It's just a personal preference for me, I really don't like a lot of the manga ones.