The most terrifying part is often the unexpectedness. Like when the ice cream truck that seems so normal at first does something really strange. For example, in some stories, the driver acts in a really creepy way.
One scary ice cream truck story is about a truck that would drive around at night with no lights on. Kids in the neighborhood heard the familiar ice cream truck jingle but when they looked outside, all they saw was a dark shape. When one brave kid went closer, the truck suddenly sped off with a screech, leaving a strange cold feeling in the air.
In another tale, the ice cream man's truck always showed up at abandoned places. His face was always in the shadows. He would drive really slowly, and his music was distorted. People who saw him up close noticed that his eyes were completely white. He seemed to target lonely kids who were lost, and there were rumors that he took them to a mysterious place and they were never seen again.
The Ice Cream Man in the story is terrifying because he breaks the normal, friendly image we have of ice cream vendors. He doesn't act like a normal person. Instead of being warm and inviting, he gives off a cold and menacing aura. His truck might be painted in dark, fading colors, and the ice creams he offers might not look as appetizing as they should. He might also have some sort of dark secret or past that is hinted at but not fully revealed, leaving the children and the readers/viewers with a sense of unease and mystery.
A really terrifying one is when a truck driver was driving near an old, abandoned asylum. His headlights flickered and he saw the silhouette of a patient running towards his truck. The figure seemed to pass right through the truck. He later found out that many people had died in that asylum.
One horror story is about an ice cream truck that would drive around a small town at night. The music it played was distorted and creepy. People who saw it said the driver had a strange, pale face and his eyes seemed to glow in the dark. Whenever kids got too close, they would feel a sudden chill. It was as if the truck was luring them in for some unknown, sinister purpose.
The idea of the ice cream itself being tainted or cursed is also quite scary. For example, if the ice cream is described as having a strange color, a bad smell, or making people ill after consumption. It turns something that is usually a source of joy, like an ice cream from a truck, into a vehicle for horror.
The sudden appearance of anacondas is often the most terrifying part. Just like in the story of the fisherman, when the anaconda emerged from the water unexpectedly. It gives no warning and can be right in front of you in an instant.
The feeling of being trapped. Once you've let the hitchhiker into your car, it's not that easy to get them out, especially if they don't want to leave. And if they turn out to be dangerous, you're in a very vulnerable position in a small, enclosed space like a car.
The most terrifying part is often the power of the acid to quickly and destructively dissolve things. Just the thought of a substance that can eat through metal or flesh in a matter of seconds is really scary.
In many scary rescue stories, the time pressure is terrifying. For example, in a rescue from a sinking car. The water is rising fast, and the rescuers have only a short time to break the window and get the people out. Every second counts, and the fear of not making it in time is huge.