Derpy came to return the jar for the fireworks to Doctor Hooves. Unfortunately, her clock caught on to Doc's secret breakthrough and she travels to the past with the background six.

The butterfly effect kicks in and leads to enough loops to get a time traveler's mind throbbing in pain.

(There's just a hint of Derpy x Whooves. Hence the tag.)
(In the future, bonus chapters through all episodes may be attempted)