Imagine your characters and world, and pick out any moment that would surprise a character. It can be small!
Describe the moment leading up to that, establish the expectation, and then reveal the contrasting reality.
In the snippet and examples above, we had:
- Scary werewolf but it's affectionate.
- Leaking roof but it's a sea-monster.
- Strawberry ice cream but it has a glass eyeball inside.
Come up with your own surprise!