When Sunset Shimmer is seeking out to find help in understanding how magic works in her human world, she looks to Equestria, but is left to find a closed portal.
Sunset calls on help from a nearby scientist to request assistance in going back who has an unusual mode of transport. A time traveling DeLorean!
During the teleportation to Equestria, the DeLorean malfunctions and sends Sunset Shimmer into an alternate human dimension. Earth!