Twilight Sparkle and Starlight Glimmer are going through a rough patch in their relationship. Sunburst is due to visit and his presence can only add to the friction.
It doesn't make things any easier when the two mares accidentally simulate a copy of the universe. One that simulates its own copy of the universe, which simulates its own copy, which simulates its own copy...
Partly based on the minific "I don't know, Timmy, being God is a big responsibility" by Twitter @qntm.