As someone who's afraid of everything, I think this prompt is really fun. Often what we fear does not match reality, and this exercise allows us to explore that.
What's something that your character is afraid of? Write a scene where your character is exposed to their fear, but the expected result does not occur. Maybe a shared secret is not met with judgement, but understanding. Maybe just when they're sure the school bully is about to throw a punch, instead, he starts to cry. Maybe what happens to your character is actually worse--much worse-- than they originally feared. Or maybe reality isn't better or worse, but just weird. Who knew that on your first anxiety ridden date with your crush, he'd confess he spent the past year living as a mime?
If you're more of a nonfiction or poetry person, explore a time when something you feared didn't turn out as you expected.
As always, feel free to share how this went!