Grass Land

Grass Land is the first world of Super Mario Bros. 3. It has six levels, one Hammer Bro. to encounter, one fortress, two Toad Houses, and a castle that has been taken over by an Airship. In level three and in the fortress Mario can get two out of the three Warp Whistles in the game. Using both of them lets him take a shortcut to World 8, Dark Land. Larry Koopa (the youngest Koopaling) guards this area and is the boss of Grass Land.

The king was transformed into a dog in the original NES version. However, in the Super Mario All-Stars remake for the SNES he was turned into a cobrat.

The Grass Land's reference is Malaysia

1-1
The first level of the game is a largely plain based level and features common enemies like Goombas, Koopa Troopas, Piranha Plants and Venus Fire Traps. This level is also the level that introduces the Super Leaf which transforms Mario into Raccoon Mario. When the player gains enough momentom at the section with the three Goombas, they might be able to fly up to a platform of clouds filled with coins and a 1-Up Mushroom. The player can fly even further to the right to reach a Warp Pipe which leads to a bonus room with coins.

1-2
This level takes place in a grassy area with many hills and also some pipes that stick out of the ground, but are unaccessible. Mainly Goombas and Venus Fire Traps inhabit the area. A variation of a Paragoomba that produces Micro-Goombas can be found at the end of the stage. Mario can make use of a P-Switch or a Super Leaf to gain access to a floating Warp Pipe located halfway the level. This will earn the player some coins. One of the many Note Blocks in that area also contains a Starman.

1-3
A plain-based level that resembles level 1-1, but features Hammer Bro.s. Two secrets are hidden within the level. The first one is a hidden passage to Coin Heaven, an area over the clouds that is filled with coins and a 1-Up Mushroom. Mario can travel to Coin Heaven via a hidden Note Block in the area with the many Brick Blocks and the red Koopa Troopa. If the Koopa Troopa's shell is kicked to the left, it will break the blocks, so that the Note Block can be revealed.

Another secret in this level is the hidden obtainable Warp Whistle that can send Mario to Warp Zone. It can be found in a concealed Toad House behind the goal. To reach it, the player has to go to the white block with the red Koopa Troopa on top, stand where the coin is located and press down on the directional pad. This will cause Mario to slip behind the background and the player can access the Toad House by slipping behind the finish.

1-4
Gold Coins and 1-Ups abound on a challenging stage of leaps and bounds. If all Coins in the level are collected, a White Toad House will appear, which has a P-Wing inside!

World 1 Fortress
A brown Koopa boss named Boom Boom defends Grass Land's stony Fortress in this level. The second Warp Whistle can be achieved by going through the entire Fortress to a door with a Dry Bones nearby; Raccoon Mario can then race back and forth on the stretch of floor by the door, eventually lifting off and going up and onto a platform high above the door and partially off the screen. When Mario gets to the end of this platform, he should press Up on the D-Pad to enter into a secret door with the Warp Whistle.

To defeat Boom Boom, the player must jump on him three times successfully damaging him, or by throwing several fireballs at him. If Boom Boom is covered in spikes, than the player should not jump on him, or else the player will take damage. When Boom Boom is defeated, he leaves behind an orb marked with a ?. When the player picks this up, a nearby locked door with disappear.

1-5
In this level, the player must delve into a dark cavern and face all kinds of unfriendly cave-dwellers. Another entrance to a Coin Heaven can be found by taking the upper route after the two Piranha Plants, then jumping against the left wall to "expose another" red Note Block!

1-6
This level isn't much different from what's been seen so far. The player must jump along platforms over gaps in order to survive. Along the way, the player can collect many coins earning the chance for a 1-Up as well as a higher score.

Larry's Airship
In this level the player must board Larry Koopa's airship. It is overflowing with cannons for an additional challenge. The player must dodge obstacles and jump over gaps, finally reaching a silver pipe in order to get to Larry Koopa.

Larry's only attack is to use the magic wand to shoot rings at Mario (or Luigi). The player must dodge the rings and stomp Larry thrice (or throw several fireballs at him) in order to win the wand back. The king of this world will then change back from a dog (NES version) or a Cobrat (GBA remake) into his normal self.

Trivia

 * In Yoshi's Safari Grass Land reappears as the first level in Jewelry Land.
 * A rendition of the theme for Grass Land is played on the Level Up Option Screen in the game Paper Mario. The same applies to the Minigame Selection screen in Super Mario 64 DS.
 * This is the only World of Super Mario Bros. 3 that does not have an alternate name.