Based on "My Overbearing Aunt" by Sketchy Unicorn; Not all transfers between Equestria and Earth were good ones, but one of the 'upper crusts' makes one certain 'bad transfer', into a new beginning.
After the Cell Games, Son Goku is sent to Equestria to be its new protector. Now granted a pass to the new world, the Saiyan is continuing his journey to become the strongest martial artist in the universe.