"One day, the kingdom of the peaceful Mushroom Kingdom people was invaded by
the Koopa, a tribe of turtles famous for their black magic. The quiet,
peace-loving Mushroom People were turned into mere stones, bricks, and even
field horsehair plants, and the Mushroom Kingdom fell into ruin.
The only one who can undo the magic spell on the Mushroom People and return
them to their normal selves is the Princess Toadstool, the daughter of the
Mushroom King. Unfortunately, she is presently in the hands of the great
Koopa turtle king.
Mario, the hero of the story (maybe) hears about the Mushroom People's
plight and sets out on a quest to free the Mushroom Princess from the evil
Koopa and restore the fallen kingdom of the Mushroom People.
You are Mario! It's up to you to save the Mushroom People from the black
magic of the Koopa!" - Official plot