It could have been a very casual picnic, but it turned otherwise. Words were exchange and Rarity accepted the challenge from Twilight and Rainbow Dash, adding another one against Applejack.
This is the story of how Rarity got Rainbow Dash to become captain of the wonderbolts.
This is the story of how Rarity beat Twilight in a magic duel.
This is the story of how she did it all in one day, using the magic of art.

But as always, the real lesson is elsewhere and Applejack won't deny it, as she was the target from the very beginning.

Because art is magic...