NDS Cheat by: Rocker99
At last, you are at the final castle of the game, but don't expect things to
be too easy! In this 1st room, go right across all the platforms while
being careful of the fireballs jumping out of the lava. At the end, go
through the door to reach the next room. In here, hit the middle block to
reveal a ? switch; hit it to flip the room, then enter the newly accessible
door.

In this room, make your way upward and to the right while avoiding the fire-
shooting blocks. When you reach the rightmost point by the door, go into the
room there. Trigger the giant Thwomp to fall, then jump over the platform as
it rises again. Hit the 3rd block above to reveal a ? switch, then continue
right.

Hit the ? block above to get an item, and hop over the left wall to hit the
switch. After the room flips, drop to the lower area and go left. Wait for
the giant Thwomp to fall and rise before crossing underneath, then enter the
next room. Make your way all the way to the far left side of the room, while
jumping over the fire-shooting blocks when it's safe to do so. Jump over the
spike pit and you will see a lone block; hit it to reveal a ? switch. Jump on
the switch to make a moving platform appear in the adjacent room to the left.

Next, go back to the right side of the room again. After you pass the
platform with the 2 fire-shooting blocks, you will see an upper ledge above
the path with the Dry Bones. Jump to that ledge and slide under the upside-
down fire-shooter to reach the door. In that next room, go up the steps after
you trigger the Thwomps. At the top, jump to the upper ledge and head left to
find Star Coin #1.

Now, go back to the right and make your way downward. Avoid the spikes as you
go down and to the left. When you are going down the steps, hit the blocks
overhead and one will yield a ? switch. Hit it to flip the room, then jump
back up the steps. Avoid the Thwomps as you reach the top area, then trigger
the Thwomp to the right. When it rises, quickly slip under it and go right.
Jump over the spike pit and defeat the Dry Bones, then enter the room below.

Here, you will see a spike pit to the left and a platform moving up and down
above it (the one you made appear before). Jump to the platform and enter the
upper-left door it leads you to. In that room, go right to find Star Coin #2,
then jump to the upper ledge and go through the door there. Go right in that
room to pass the midpoint finally, then hit the ? block ahead to get an item.

Go right and you will see 3 levels of platforms you can travel on. If you
remember the original Super Mario Bros., you will know that you have to get
through this next section by traveling the different levels in a certain
order, or else it'll loop infinitely. If you took the right path, you will
hear a ding; if you took the wrong path, you will hear a heavier sound, and
you will have to start from the beginning.

Anyway, for this next part, take the bottom path, then the top path, and
finally the middle path. If you did it right, you will be able to continue
onward. Below you will see Star Coin #3 in the corner. Ground pound the
blocks to the right of it, then go into the corner and grab the coin. Jump
through the thin ledge and continue right to the boss door. Go inside and
head right to meet up with Bowser and Bowser Jr.

The fight will now commence against both father and son, together. Your 1st
priority will have to be Bowser Jr. He will jump and charge at you, and you
are not allowed to jump on him normally because of the spiked shell. Wait for
Bowser Jr. to throw a green shell, then toss it back at him, and jump on his
belly to cause damage. Do this 3 times and Bowser Jr. is done for. While
you're dealing with Bowser Jr. though, regular-sized Bowser will slowly move
towards you while spitting fireballs.

After you beat Bowser Jr, the Resurrected Bowser will start shooting several
fireballs at once in various directions. Stay back, then jump to avoid the
lower-flying ones. He will sometimes shoot 3 blue fireballs at you: one
straight ahead, and the other 2 will go in each of the diagonal directions.
All you need to do is wait for Bowser to jump in the air. When he does,
quickly dash under him and step on the red switch to remove the bridge,
finishing him off in such a traditional fashion.

Following the fight, you will be reunited with Princess Peach, and the
credits will begin to roll. Congratulations on playing through and beating
the New Super Mario Bros. game!