Noticing the bird netting (to keep deer away) all bunched up over my carrot plants, I started gently pulling the netting away from the carrot tops. Concentrating on gentle twist by gentle tug, I discovered the white belly-up dead chipmunk laying in my hand. Ah ha! The reason for the bunched up netting. But rather — AHHHH! A dead chipmunk in my hand! I dropped the corpse in the twisted plastic and danced my way into the house to wash up, wiggling every muscle in my body along the way. I shiver now just remembering it.
The willies. I got them. Suddenly. Unexpectedly. Admit it. We all get them. I get them at other times, too, more than about unexpectedly finding dead critters in my hands. So, how about you? Give it a moment. What do you get the willies about?
Now let’s turn to the what-if with character development. Imagine the boxer Rocky just finishing his first big fight and everyone is cheering and suddenly and unexpectedly a spider drops onto his shoulder, and imagine that this powerful hero who reached his goal is also deathly afraid of spiders. I suppose giving Rocky the willies would have taken away from the joy of victory or the focus on a strong hero-type in the movie, which would defeat the Hollywood set. On the other hand, it sure would have rounded out his character, which is exactly what novelists do.
So go to your hero or heroine. Give him or her something to have the willies about. Make your MC more real by also laying a creep-factor on him or her.