Have some Joseco Derpy because I don't have any Big Mac or Cheerilee on hoof.
AT&T's Uverse has put up an extended version of the summary for Hearts and Hooves Day. Slightly more information ahoy! Find it after the break.
Hearts and Hooves Day
The Cutie Mark Crusaders create a strong love potion in the hopes of making Miss Cheerilee and Big Macintosh fall in love, but when they discover the serious side effects of their concoction, they quickly regret their actions.