Locate the red flower in level 1-4. Shoot the coyote that attacks from behind twice while jumping to display a power-up in the form of a Nintendo controller. Get the controller to collect 1000 points. You only have to shoot him once after you jump but you have to shoot him before you jump over him
1-1, section 3: Stand between the fourth and fifth totem poles and wait for the platform to appear.
1-3, section 2: Look for the key egg right on the ledge just before the dropping platform. Once you have the key the platform lifts you to a bonus level instead of dropping.
2-3, section 2: The key egg is on the stone section right after the "2" sign. After that, the third platform lifts you to the bonus level.
3-1, section 2: Pass the two frogs and jump down two more steps to a long flat area. Run around and toss your weapon around and eventually the platform leading to the bonus area will appear.
4-3, section 4: Jump to the third ice-tower, and jump to find the key egg. The next moving platform takes you to the bonus area.
5-1, section 1: The key egg is just before the cloud platforms, and the last cloud platform then takes you up to the bonus area.
6-2, section 1: Jump over the rolling boulder and then wait around for a little bit for the bonus platform to appear.
8-1, section 3: Stand in the area between the rock with the hidden pot and the egg with the eggplant inside.
Near the end of the first level, before a sign that says ''G'' on it, jump up at the edge of the cliff that's after the platforms. If you find an egg (that contains a bee), you know you've done it. At any Game Over screen from now on, hold UP, A, and SELECT. Then press START. You should repappear in the start of the level you died at with some extra lives. This game has a few versions and the code only works for some versions, oddly enough.
Allow the game to reach the title screen, then reset the NES console. Then, press Right, Left, Right, Left, A, B, A, B when the title screen appears again for a level select. I have tried this it does not work it just starts me at 1-1. This does work on Adventure Island 2
When you defeat the first boss, pause the game as the first boss leaves the screen. You'll be able to see the next boss.