New Super Mario Bros./World 7-3

You may have met Wigglers back in World 4, creatures that are basically giant caterpillars. Now meet the Mega Wiggler, a giant of giants, a humongous life form so big that it stretches across several screens. You'll be needing this docile beast to cross a giant abyss, as Bowser Jr's troops ambush from above. Get a Star chain going for some seriously long invincibility, and even a load of 1-Ups!

Level walkthrough
The starting area consists of two Wigglers. Ignore them and head for the green pipe. Go down it to enter the main portion of the level. As you come out of the pipe, a Mega Wiggler will charge forward below you. Drop down on to the Wiggler and stay on it. You should pass by some Paratroopas and a bunch of coins, including ones created by touching the outlines of the coins. There is also a red ring that can only be reached when the Wiggler's body shifts upward. The red coins it generates are arranged linearly in front of you.

You will pass by several more coin outlines, as well as a pipe that spawns Goombas. The Goombas can move freely on the Wiggler as well, so it would be wise to take them out. Later, you'll come across a Boomerang Bro. on a brick block platform. The safest way to defeat it is by hitting it from below. After that, get on the platform and jump up to the first Star Coin. After that, Goombas will start to drop from the sky. Meanwhile, more coins can be collected from touching the many coin outlines in the stage.

There will soon be a lone block on top of a trio of blocks. Hit the single block to make a Star come out, the first of several you can chain together. While invincible, you actually create a trail of silver coins wherever you run, which can let you gain a ton of money, as well as more than a few 1-Ups. The next few blocks in your path all contain Stars if you're still invincible, so you can keep a chain going if you're quick enough. You will soon see a Star Coin on a high platform. You need to jump when the Wiggler's body is at its highest part, which can waste your invincible time if you're not skilled enough. Nevertheless, you should still attempt to get it for the sake of completion.

One more block containing a Star and several more enemies are all that remains until the end of the level. The pipe to the exit is guarded by a Boomerang Bro., which can be taken out with no trouble if you're still invincible. Enter the pipe to arrive at the flagpole area. You should notice some brick blocks forming steps as you go right. Ground pound the left most block to make a vine grow downward, then ground pound any of the other blocks and climb the vine down. Jump to the right when you see an alcove containing the final Star Coin. Take the pipe back to the top and jump to the flagpole to finish the stage.

Star Coins

 * 1) The Star Coin is above a brick block platform, guarded by a Boomerang Bro.
 * 2) This Star Coin is floating above a pretty high platform. Hop off a Paratroopa or use the wave in the Mega Wiggler's movement to jump up to it.
 * 3) In the flagpole area, ground pound the leftmost brick block to make a vine grow into it. Ground pound any of the other blocks and climb down the vine to find the Star Coin.