He found your body in an accident and he removed your brain and placed it in a jar

*you were walking and bump into each other and now you control either the upper or lower half of her also you're co-workers* her: "wha-what just happened"

wants to swap bodies with you

she is your gf of 5 minutes and she has no hands

turned you into a baby

10,000 year old witch turns you into an animal (age of animal changes to reflect the lifespan) after you wake her up by walking through the woods

earth

it is 1987 you see a witch