Fluorescence's mom runs the pony side of the portal between Equestria and Earth. Taylor's mom runs the human side. So Fluor and Taylor have been friends forever. This only occasionally leads to interdimensional disasters.
The planet Equus will be inhospitable in just a few short years. All the creatures on it are preparing to leave for greener pastures. All, that is, except Spitfire.
Snapshot is a mare who survives in the walled city of Neo Somnambula by working at a brothel. Despite her debt, Snapshot still tries to follow her dreams of being a photographer.
Lightning Dust strands her rocket in space. She'll die unless Equestria's Best and Brightest find a way to bring her home despite sabotage, snobbery, limited resources, and bureacratic incompetence.
Miner Derpy Hooves is sent deep into the crust of the planet Hockses to kill bugs, defeat interloping rival corporations, drill for precious resources, and mine like her life depended on it (which it does)