Super Mario Brothers
Continue game play:
Hold A at the game over screen. While keeping that
button held, press Start when the title screen appears.
Alternatively, hold A and press Start(2) at the
title screen.
Fireworks:
Hit the flagpole at the end of a level when the last digit
of the timer is 1, 3, or 6.
World -1:
Stand on top of the exit pipe on world 1-2 and scroll the
screen as far right as possible. Run to the right, then back to
the left as far as the end of the pipe, then back again several
times. The screen to reveal a blank space on the far right side
of the bricks. Jump up and break the only second and third bricks
from the right. Place Mario on the pipe with one foot off the
edge and face him to the left. Press A to jump, and press
Right while he is in the air. Do not break the remaining
brick. The back of Mario's head should hit the brick and pull
him in. Walk through the bricks to the right and immediately enter
the first pipe on the left.