A wave of invisible energy passes over the world, causing people to suddenly and randomly swap bodies.

Describe your character and what they were doing before the shift, let the AI come up with the rest.

The Great Shift: a wave of invisible energy that washed over the entire world. It caused most people to suddenly and randomly swap bodies with a person nearby. If two people were touching during the shift they almost certainly swapped bodies. The great shift effects 93% of the human population.