Classic NES Series: Super Mario Bros. Hints & Cheats

Go to world 1-2.
At the end of the level, there is a pipe, and some bricks.
You must smash the second to last brick and the third to last brick as seen to the left.
Now you must stand on the edge of the pipe, duck, and face left
Now jump to the right towards the one block that you didn't break, while facing left
You should slide right through the bricks, go into the first pipe when you get to the other side.

You should be warped to the minus world, the level is -1.

In order to get fireworks to go off after you beat a level, simply finish the level when the last number in the Time is either a 1, 3, or 6. The number of fireworks you get depends on that number. So finish a level with 106 remaining, and you'll get 6 fireworks to explode. Plus, you get bonus points for each firework that goes off.

During World 1-2, go to the end of the level and get on the rising platforms. Now jump onto the TOP of the level and go right until you reach three pipes. You can now warp to either World 2, 3 or 4.

In world 4-2 you will come across a moving platform. Jump past the platforms until you see a ledge with three blocks. Go just left of the first block and jump, you will reveal a secret block. Go over under the second block and jump (rember to leave the space under the first block empty) and jump under the third block to reveal another hidden block. Jump on top of the blocks and start destroying the blocks until you find a vine growing out one of them. Climb up the vine to reach an area with lots of coins. go right until you find some stairs. jump on top of them and walk rigth. Now you can warp to levels 6, 7, and 8.

If you ever find yourself with a Game Over, and you would like to continue from what world you were on, wait for the 1/2 Player select screen, then hold A and press Start. Now you will start at the first level of the World in which you obtained the Game Over from. For example, if you got the Game Over from 7-3, you will start over again at 7-1!

At the end of World 4-2, jump onto the top of the screen and keep walking until you drop into a room with a warp pipe. It leads to World 5.

Go to either 1-4, 2-4,3-4, etc. and get to Bowser. Make sure you are Big Mario and try to jump over Bowser or run under him. Stand near the Axe and Bowser will start to walk towards you. As he gets near you, jump high, and touch Bowser and the Axe at the same time. If you do it correctly, you will hear the sound as if you were to shrink, but you will just flash and stay as Big Mario. Go to the next stage, and get a Mushroom. (Yes, there will be a Mushroom instead of a Fire Flower.) When you touch the Mushroom, you will shrink. Then get a Fire Flower, and you'll have Fire Power as Small Mario. (Note: after you do the Bowser/Axe trick, enemies that touch you will be able to kill you when you are Big Mario. When they touch you while you are Small Mario after getting the Mushroom or Fire Flower, you will turn back into Big Mario.)