Reversals change the meaning of something by changing the context. In other words, part of the meaning of anything we consider is due to its environment.
In storytelling, we can add surprise to a story by leading the reader or audience to perceive something one way, than shift the context to show that it is really quite different.
For example, there is an old Mickey Mouse cartoon called Mickey’s Trailer which opens with Mickey stepping from his house in the country surround by blue skies and white clouds. He yawns, stretches, then pushes a button on the house.
All at once, the lawn rolls up, the fence pulls in and the house becomes a trailer. Then, the sky and clouds fold up revealing it was just a painted backdrop and the trailer is actually parked in a junkyard.
In your own story, look for opportunities to liven things up by intentionally creating a false first impression and then reversing it when more information is provided.