Ponyville's premiere prankster pair, Pinkie Pie and Rainbow Dash, are faced with a dilemma as the April Fools' day approaches. Can they come up with a joke to top all the jokes they've pulled in previous years? Will Pinkie's rapidly expanding waistline cause a rift between the friends, and who's going to take responsibility? Why is Fluttershy, of all ponies, so disapproving of the situation?