World 4 (New Super Mario Bros.)

World 4 is a world found in the game New Super Mario Bros. This world is mainly forest-based, and features a type of purple coloured toxic water, which kills Mario and Luigi with a single touch - regardless of what form they take.

This world is accesible by defeating Mummipokey from World 2 in Mini Mario form. World 4 introduces a lot of new enemies, such as Wigglers. It also introduces Dorrie - a friendly creature who helps the Mario bros. travel along the toxic water. As with all the other worlds, Bowser Jr. is fought here. The Boss of this world is Mega Goomba.

4-1 (Dorrie's Safari)
In this level, strange purple goop covers the ground. If Mario touches it, he will instantly lose a life. To start, Mario should keep walking until he finds some Scuttlebug. He should jump on them to gain a jumping boost, which is used in collecting the first Star Coin. About halfway into the level, the player should see a Dorrie. Jump on it to ride it, while avoiding the Scuttlebugs. Mario does not need to ride the Dorrie as he can simply make long jumps and bounce off the Scuttlebugs and stand on blocks in between them. To get the second Star Coin, Mario again should get a jumping boost from the Scuttlebug. After getting off Dorrie, Mario should jump onto the donut lifts to avoid falling into the goop. The final Star Coin can be obtained by using a Koopa Troopa and throwing the shell at the coin. After this, Mario reaches the Flagpole.

Secret Exit
While Mario is riding Dorrie, the player should notice that on the way, there are two ? Blocks with three normal blocks in between. If Mario gets on top of them and jumps in the middle, a Beanstalk will appear. Climb on it and enter the pipe to reach the Red Flagpole. The secret path opens up a Toad House and takes the player to 4-Tower.

Star Coins

 * Star Coin 1 - Jump off one of the two Scuttlebugs to reach the first Star Coin.
 * Star Coin 2 - While riding Dorrie, jump off one of the Scuttlebugs again to reach the second Star Coin, but while taking caution of the toxic water.
 * Star Coin 3 - After hopping off Dorrie, there should be two Scuttlebugs and a brown block formation. Kill both Scuttlebugs and carefully traverse the Donut Lifts and toxic water.

4-2 (Sky Rocks)
This level has purple mushrooms that, when Mario stands on them, tilt to the side he's on. Move quickly to avoid falling off of them. The first Star Coin can be obtained by Wall Jumping to it. To get the second Star Coin, Mario must let one of the purple mushrooms tilt to the right. Once the player gets it, jump off to the next mushroom. Soon after the coin is a Red Coin Ring. Mario will come to a stepped platform. Jump on the purple mushroom after it, let it lean to the left, and jump over to the brick and hit it to reveal a Beanstalk. Climb it to go to a bonus area. Go up to find the third Star Coin. Then the player should go through the Warp Pipe and get to the Flagpole, ending the level.

Star Coins

 * Star Coin 1 - Wall jump off the side of a rock formation and grab the coin while avoiding falling down.
 * Star Coin 2 - Tilt the purple mushroom with a red Koopa on it and quickly jump off it to reach the Star Coin and safely land on the nearby green mushroom.
 * Star Coin 3 - When Mario or Luigi reach an area with a stepped platform, tilt the nearby mushroom to the left and hit the Brick Block to reveal a Beanstalk. Hit yet another block to reveal another Bean Stalk. Grab the Star Coin and leave the area.

4-3 (Unagi Cove)
This level takes place underwater. Go into the pipe and start swimming. Soon, the level will start auto-scrolling. Maneuver through the water while avoiding the Regular and Mega Unagi. The first Star Coin is in a little crevace about a quarter into the level. After the coin is a Red Coin Ring. The second Star Coin is found about halfway into the level between two Unagi. If the player presses the ? Switch and then goes into the green pipe that is next to the yellow pipe, they will find the final Star Coin. After going through the Exit Pipe, Mario will reach the Flagpole.

Star Coins

 * Star Coin 1 - After the first Mega Unagi passes, swim to the right and go under a rock formation to get the first Coin. Speed is vital because if the player is not fast enough, Mario will be crushed by the scrolling screen and rock.
 * Star Coin 2 - This Coin is located at the bottom of the level, but is guarded by two Unagis.
 * Star Coin 3 - After hitting the ? Switch swim and enter the lower right green pipe to be transported to an area with two Unagis and a red pipe spewing bubbles. Swim over the cave of the Unagis and use the bubbles to get the Coin.

4-Tower (Bowser Jr.'s Fortress 4)
This level is filled with lava. Mario should jump on the moving gray blocks to get to the door. In the next area, lava rapidly rises. First, get on the other side of the metal fence. If the player stays to the left, he/she will eventually reach the first Star Coin. The second Star Coin is in between a few Amps. Next, Mario should avoid the spikes, and continue climbing. If Mario stays to the right, then he'll find the last Star Coin. A Red Coin Ring is found near the end of the level. This time, Bowser Jr. will be harder to defeat. If the player tries to jump on him, he'll go inside his spiky shell. Wait until he throws a Green Shell. Then, Mario should jump on the shell to stop it, and he should throw it at Bowser Jr., which stuns him. Only then can Mario jump on him. Doing this three times will defeat Bowser Jr.

Star Coins

 * Star Coin 1 - Flip to the back side of the fence and the first Coin should be on the left side of the second area. Make sure to flip back as soon as possible.
 * Star Coin 2 - Stay on the right side of the level and the second Star Coin is guarded by two Amps.
 * Star Coin 3 - Make sure Mario or Luigi are on the front side of the fence. Take the right side of the path and the Star Coin should be in easy reach, but be careful with the rising magma.

4-A (Toxenom Lake)
This level has more toxic water in it. To begin, Mario needs to swing on the vines in order to get to each platform. The player should soon see a Pinwheel, and then he/she should use it to again jump onto land. When Mario finds a Paratroopa in the way, jump on it to get a boost. Use this skill to get the first Star Coin. This is also used to reach some faraway ledges. To get the second Star Coin, use a Paratroopa to bounce up to a vine above him. Swing into the Warp Pipe to reach a cave with the Star Coin inside. The player should notice three pipes together (green, yellow, green). Enter the lowest one to get the third Star Coin, after this, Mario reaches the Flagpole.

Star Coins

 * Star Coin 1 - Near the middle of the level, jump off the Paratroopa to get the Star Coin, but be sure not to fall into the water.
 * Star Coin 2 - Jump off a Paratroopa to reach a vine and then enter the nearby Warp Pipe. Hit the P Switch and kill all the Koopas before getting the coin.
 * Star Coin 3 - Enter the lowest pipe aformentioned, but be careful with the Piranha Plants that lurk inside.

4-4 (Wiggler Rock)
This level features a lot of Wigglers. Mario can complete the Red Coin Ring by getting a boost from a Wiggler. The first Star Coin is found in a little cave near a Wiggler. Later, Mario needs to hit a block that contains a Beanstalk to climb up it and continue. If the player goes left and Wall Jumps off the wall, they will find the second Star Coin. The last Star Coin can be obtained by sliding on a wall next to it, then Wall-Jumping to the small pipes. After going through the Yellow Pipe, Mario reaches the Flagpole.

There is a very secret area in this level, reached by using a Mini Mushroom to go down one of the small pipes - the second from the left where four are together, with a Wiggler on top. This secret area has a Mega Mushroom, and a lot of pipes to smash, along with some coins to collect.

Star Coins

 * Star Coin 1 - Throw the red Koopa shell against the left wall so it bounces off the wall and takes out the Wiggler along with itself. The Star Coin requires precise wall jumping.
 * Star Coin 2 - After reaching the area with a Random Block, climb the beanstalk and head to the left. Next to the Brick Block is a hidden beanstalk. Climb it to reach the next star coin.
 * Star Coin 3 - Carefully slide down the wall of a cliff and then wall jump to some nearby mini pipes.

4-Ghost House (Spin House)
To start, Mario should step onto a striped platform that takes him past a wall. The first Star Coin can be found by going up past the blocks and right to another striped platform where he will find the coin above it. After the platform, Mario should press the ! Switch and go through the door, avoiding the Balloon Boo along the way. To get the second Star Coin, Mario should press another Wall Jump on the first red blocks he sees (for the third Star Coin, see "Secret Exit") and go up. Then, the player needs to jump on the blocks, past the first door (if Mario goes through the first door, it will take him back to the start of the area), and into the second door. This will take Mario outside, to the Flagpole.

Secret Exit
To access the Secret Exit, the player needs to be Mini Mario. When Mario reaches the area with the second Star Coin, Mario should get onto the pipe, not entering it. Then, he should Wall Jump on the pipe, reaching a faraway door. By continuing to Wall Jump and by going up, Mario will reach the third Star Coin. Going through the door takes Mario to the Red Flagpole.

Star Coins

 * Star Coin 1 - Enter the door in the beginning of the level and hit the ? Switch. Four blocks attached with strings will drop from the ceiling. Hop on top of one of these and when it goes up, the player will be transported to the first Star Coin.
 * Star Coin 2 - Using some red blocks, Wall Jump off them to reach a higher area and where the Star Coin is found.
 * Star Coin 3 - Jump off the aformentioned pipe onto the above platform as Mini Mario or Luigi. Keep wall jumping until the player finally reaches the Star Coin.

4-5 (Bob-Omb's Cave)
This level is an underground level with Bob-ombs. Some bricks can only be destroyed by blowing up a Bob-omb. This is needed for Mario to get past some areas. This skill is also used to get the first Star Coin. To get the second Star Coin, the player must wait until a drawbridge goes up. Next, he must hit the Bob-omb above him, destroying some blocks, allowing him to get the coin. After a few more drawbridges, the player should notice one that has a pipe with blocks covering it. If Mario blows up a Bob-omb, he can go inside it and, by breaking more blocks with Bob-ombs, he can get the last Star Coin. Leaving the Warp Pipe is the Flagpole.

Star Coins

 * Star Coin 1 - Place a Bob-omb near the side of the box to blow it up and reveal the first Star Coin.
 * Star Coin 2 - When the drawbridge goes up, hit the Bob-omb and wait till it bloes up. Nab the coin and continue onward.
 * Star Coin 3 - Blow-up the blockage of the pipe with a carefully placed Bob-omb. Once inside, blow up the bricks with the Bob-ombs to reach the last coin. However, there are only 5 Bob-ombs located here, so preciseness is vital.

4-6 (Poison Sea)
In this level, Mario will ride another Dorrie, avoiding yet more toxic water. To get the first Star Coin, Mario should jump onto land, past the Red Coin Ring. When on land, the player should keep up the pace with Dorrie. The second Star Coin is obtained by pressing a P-Switch and jumping on it. Soon, the player should see a ! Switch. Mario should wait for Dorrie's head to go up, and then he should jump and press the switch so he can go into a pipe that contains the final Star Coin. Soon, Mario should reach the Flagpole.

Star Coins

 * Star Coin 1 - Jump onto the area directly after the Red Ring to get the Star Coin.
 * Star Coin 2 - Hit the P Switch to turn all the nearby blocks into coins, where the Star Coin will be easy to reach.
 * Star Coin 3 - Hit the red ! Switch and quickly enter the pipe. Slide down the slope while taking out all the enemies. The Star Coin is in the middle of a mass of coins.

4-Castle (Mega Goomba's Castle)
The player will start off on a ledge. They will see a platform that will swing from left to right, along with a ? Block containing a coin. The player will see coins floating in the air, aswell as another ? Block, this time containing a power-up. The player will now have to jump on another swinging platform, which will have a Dry Bones wandering on it. A Podoboo and another swinging ledge with a Dry Bones can be seen. If the player jumps when the swinging platform is at it's max height, they will get their first Star Coin. The player will fall down, and see a Dry Bones along with two ? Blocks, containing coins. Now the player will see a couple of Thwomps. The player can take two routes from here, either Wall Jump while collecting coins, or jumping from platform to platform while avoiding a Thwomp. In the lone platform, there is a Hidden Block with a Star inside of it, along with two visible one's containing coins. The player will see a couple of Dry Bones and a Super Thwomp. If the player waits while the Super Thwomp is crushing the blocks, they can get their second Star Coin. The player will find a ? Block, containing a power-up. The player will meet up with more Thwomps and Dry Bones, aswell as another Super Thwomp. The player will collect some coins and find a Dry Bones here. The player will now be at the checkpoint area, and see a ? Block containing a power-up, a Podoboo, and another ? Block which will have a 1-Up Mushroom. The player will be on a swinging platform, and see their last Star Coin. The player must jump from the swinging platform to another, while avoiding a Dry Bones and many Podoboos. The player will now see a boss Door, and will fight Mega Goomba. After the player has defeated it, they will now have access to World 5 (NSMB).

Star Coins

 * Star Coin 1 - Jump off the platform when it's at its max height to get to the Star Coin on a ledge.
 * Star Coin 2 - Have the Super Thwomp destroy the three rows of blocks that guard the second Star Coin.
 * Star Coin 3 - After getting on the swinging platform, jump off it to land on the ledge below where a Star Coin is.

Enemies Introduced

 * Scuttlebug
 * Unagi
 * Mega Unagi
 * Bob-omb
 * Wiggler
 * Thwomp
 * Super Thwomp
 * Balloon Boo