Game Genie Cheats
The easiest way to cheat and complete the castle in Level 7 of Super Mario Brothers 3 is by entering codes into your Game Genie system. The Game Genie attaches to the Nintendo cartridge and allows you to enter three cheat codes. You can grant yourself unlimited lives, the ability to fly at all times and even invincibility. Since there is only one enemy in the fortress in Level 7, you will need the "Skywalker" cheat only.
Coin Room
When you first enter the fortress, you find yourself in a massive room made entirely of bricks. Notice the gray platform ahead of you. Walk to the fourth column of bricks past this platform, and break the column above you. The last block is a switch block, which you can jump on to turn the entire room into coins. Jump on the block and collect as many coins as you can before time runs out. If you want to repeat this process, exit the door at the bottom of the room and immediately re-enter.
Hidden Tanooki Suit
If you have a leaf in your inventory, use it before entering the fortress. You will need flying power in order to complete this castle. If you don't have a raccoon or Tanooki suit, you can acquire one inside the fortress. In the coin room, you can make a secret door appear by jumping on the switch block. Instead of jumping through the room to collect coins, jump to the gray platform to your left. Enter the door on the platform. In the next room, enter the first gray pipe. You are now in a room with an oversize brick. Hit the brick to collect your Tanooki suit.
Finding the Boss Arena
As with all castles, you have to defeat a boss. If you have flying powers, you can skip right to the boss arena once you are finished collecting coins. Enter the door at the bottom of the coin room to move to the room with a checkerboard floor. This room is abandoned, so don't worry about enemies. Fly to the left, and look for a pipe in the ceiling. Enter the pipe and you will now be in the boss arena.