New Super Mario Bros./World 4

World 4 is one of two possible worlds that come after World 2, as well as one of the two secret worlds that require a special requirement to unlock. Compared to its counterpart, World 3, it has about the same amount of levels but less split paths, making the World seem overall longer. It also has much more Toad Houses, but most of them are locked behind Star Coin signs.

Level summary

Level	Star Coins
World 4-1	This coin is out in the open, above a pair of Scuttlebugs. Jump off one of them to bounce up to it. The coin is suspended in midair during the Dorrie section. Get on the brick blocks before it, then jump as Dorrie moves below you to land on it safely. Inside a wide valley surrounded by Scuttlebugs and above poison water. Defeat the Scuttle bugs and dash across the donut lifts to get it.
World 4-2	The coin is plainly visible, high in the air. Wall jump off the stone wall to the left to reach it. This coin appears soon after the first. Tilt the purple mushroom platform to the right and quickly grab it before jumping off. When you reach a large stone platform with a lone brick block in the floor and some coins in a crevice underneath, get below the brick block and hit it to make a vine extend. Climb up the vine to head to a secret area, then hit the block there to make another vine, one that lets you get the coin.
World 4-3	This coin is in a crevice, shortly after the first Mega Unagi. Get it quickly to avoid getting crushed by the auto-scrolling screen. The coin is found soon after the checkpoint flag, positioned between two Unagis. Carefully sink between them to obtain it safely. After hitting a P-Switch, go through the rightmost warp pipe nearby to enter a secret area. Go anti-clockwise around the center block to grab the coin.
World 4-Tower	Make sure you are on the backside of a fence before seeing any Star Coins. Once you see the first moving stone block in the rising lava section, Go left past it. The coin is behind a fence. Soon after the first Star Coin, stay on the right side of the screen. You can see the coin soon, and you must jump from the fence below between the Amps to get it. Stay on the right side of the screen as you encounter some horizontal moving stone blocks. The Star Coin is at a vertical dead end. Duck on the nearby stone block once you collect it to make a quick escape.
World 4-A	The Star Coin is easily visible in the air. Jump off of the Paratroopa nearby to obtain it, making sure to land on the rotating platform afterward. Jump off another Paratroopa after the first coin to get to a vine. Swing up to a warp pipe, which takes you to a cave. Get on the rectangle block formation and press the P-Switch to access the coin within. Near the exit pipe are three pipes next to each other. Go down the first to enter an underground area with the coin.
World 4-4	The coin is in a crevice guarded by a lone Wiggler. You can either knock it out by bouncing a Koopa shell into the pocket or just evade its charges as you go for the coin. Use wall jumps to go in and out of the crevice. Move left after climbing the first beanstalk to find a pit with a Wiggler. Jump up the space to the left of the pair of blocks to hit a hidden beanstalk. Climb it to get to the Star Coin. This one is suspended in midair near a bottomless pit. Slide down the wall to the left of it and wall jump off once you touch the coin. Alternatively, grab a Koopa shell and hop to the pipes to the right of it, then toss the shell at the coin.
World 4-Ghost	Go in the first door you see and hit the switch. Stand on one of the blocks that fall down, and wait for them to go back up to be transported to another area. Go right to get the coin. After heading through the one way door, go left and hit the red switch, then wall jump up the two columns of blocks to the ceiling. The coin is easily within reach here. You'll need to be in Mini form for this. In the same area as the second Star Coin, hit the red switch and use the blocks that form to get on top of the entrance to the warp pipe. Wall jump off the pipe and on to a platform on the right. Keep going up with wall jumps, ignoring the door, until you can get the coin.
World 4-5	This coin is surrounded by solid blocks next to the ground. Have a Bob-omb blow the blocks up. The star coin is in a compartment above a bridge. Knock the Bob-omb down to blow a hole into the compartment, letting you jump up and collect the coin. Next to a Bob-omb spawning pipe is a blocked pipe entrance. Blow up the blockage and enter the secret area. Carefully plan explosions using the Bob-ombs inside to create a path to the coin.
World 4-6	The star coin is on the second island Dorrie passes, well within reach on land. The coin appears soon after the checkpoint, next to a P-Switch. Hit the P-Switch to turn the nearby blocks into coins, making it easier to collect the star coin. Hit the red switch on the ceiling as you pass by it, then hop to the pipe entrance with two red blocks beside it. Enter the bonus area and go right to collect it.
World 4-Castle	On the last swing platform before the Thwomp corridor, wait until it swings to the right. Jump off the swing and land on the stone ledge to get this Star Coin. Have the first Super Thwomp destroy the blocks below it. Fall into the gap to get the Star Coin. This coin is right below one of the swinging platforms in the latter half of the castle. Hop on to the thin platform the Star Coin rests on once the swing is fully angled.

Secret exits

World 4-1

During the Dorrie ride, wait until you approach the third set of brick blocks, which also happens to be the longest. Get on the brick blocks and stand in the middle. Jump directly up to cause a vine to pop out, which leads to a platform with a pipe in the canopy of the jungle. When you emerge, jump on to the hills and try to leap over the trio of Scuttlebugs to reach the top of the red flagpole.

This secret exit lets you bypass two levels to get to World 4-Tower, granting access to a green Toad House along the way.

World 4-Ghost

You'll need a Mini Mushroom to get to this secret exit. After hitting the second red switch, head on to the pipe with red blocks beside its exit. Instead of heading through and progressing as normal, hop on the top of the warp pipe. Wall jump off the pipe and to the right, where there is a ledge that is otherwise inaccessible without the floaty jumps of Mini Mario/Luigi. Jump up and into the gap above. You will emerge in another room. Ignore the door first and keep using Mini Mario's wall jumps to get the last Star Coin. Fall back down and go through the door to be taken to the red flag.

This hidden exit leads to the World 4 Cannon, which blast you far above the canopy and into the cloudy World 7.