Before I begin my review, I have to ask: what does the episode's title have to do with the episode itself? It's not even a very eye-catching or interesting title, either (neither is your banner).
AND NOW, MY REVIEW OF SUPER MARIO 16 X
Before the episode is even started, there are a couple of prevalent errors: 1)The title is misspelled on the episode select list (it says "Mariio" instead of "Mario") and 2) you left not one, but two save files in the upload. Why is it so common for people to leave save files in the episode when uploading? It just puts more work on the player because the save files need to be deleted to start a new game.
When starting the episode, the player is greeted with a text dump with the same "go fight Bowser" story that comprises most Mario games, only there are a few typos here as well. 1) There should be a "the" in between "to" and "World," 2) the "b" in "bowser" should be capitalized, and 3) there should be a comma before "Too." Also, the "T" in "Too" should be lowercase.
Before I move on to talking about the levels, I'd like to show each instance of what I call a warp-chain.
And now, I will show each instance (that I found) where the player can jump over the ceiling:
One final list; this time, it's almost each instance of cut-off (I say "almost" because some deserve their own spoiler):
To fix most of these, sprite swap a background image to look like the cut-off tile and put it behind the tile cutting it off.

In this case, you could just reverse the direction of the SMB1 split-pipe block (block-378), have that sprite swap the
original block, and use that here instead:

Some instances of cut-off consist of what are already background images, so it wouldn't take much effort to put them behind the blocks that are cutting them off.

Um...you used the wrong Super Metroid door block here:

However, that's not the only instance of using the wrong tile. For instance, here, you used the 32x32 slope-curve block instead of the 32x64 slope-curve block.

Here, you didn't use
any slope-curve blocks. I know they exist, so why didn't you use them?

Anyway, the first level is unremarkable, except for the warp-chain and the pointless sign (it doesn't have a message), so on to the second level: it's also pretty unremarkable, except for this:
I thought the water indicated some sort of secret, so I jumped down there and died. I suggest removing the water entirely.

Next level: there are quite a few warps that do this:
Like this, it looks like Toad is getting his head sliced in two by the pipe. Just move the warp half a unit down to fix it.

But...but I just passed up a star on my way here! What's the point of this?

World map tip #1: don't put paths right by each other if they shouldn't connect. Otherwise, this happens:
Moving on:
What are you talking about? It's night, not evening!

This is my favorite part of the episode. It's random, but still relevant (unlike some other stuff in the episode, which I'll get to later).

On the contrary, this is my least favorite part of the episode. After exiting the pipe, that green fish at the top left is literally right on top of the player, and an unfair and unnecessary hit has to be taken. The player-character is invisible because I took the screenshot when he was flashing. Remove that fish entirely.

Speaking of fish at the top left, the one here is stuck in that corner of the blocks and can't move (during game-play, it was constantly switching between its left-facing frame and its right-facing frame).

Something else I don't like are your vanilla block-houses. There are perfectly good sprite-swaps for mushroom houses in the GFX pack; use those instead.

All right, on to the desert level:
As you can see, that tiny pipe is too small for those large Piranha Plants. You should give them a bigger pipe.

Also, you should probably put a secret here or something because it's entirely possible to make it down here without getting hurt.

On to the first castle level:
What is the purpose of this single dark tile in the middle of all of the light tiles? It doesn't look good.

Well, an Iggy Koopa fight was foreshadowed twice before in the level, so yes, I did think that it would be easy.

This is nonsense:
Even ignoring the bullet bill cannon wall at the beginning, there should be some way for the player to obtain a shell in case the others are killed or off-screened, like a paratroopa generator.

Also, I thought this was a warp pipe (because otherwise, it would be a poor design choice), and I ended up getting stuck and was forced to die.

This is also nonsense, and what I was referring to earlier in my review. You're trying to be funny, but you went completely overboard with the randomness and it just ends up being confusing. Plus, the "d" in "dis" should be capitalized; it's common grammar.

NO! It doesn't matter how many times you repeat it or what dumb custom "song" you have playing; IT'S NOT FUNNY!

...I'm not completely sure you know what these background images are for...
They're meant to go on top of the SMW log platforms (block-446). I'm not too sure what they're supposed to represent, here.

World map suggestion #1: name everything. If something doesn't have a name, it looks weird:
There may be an instance where it would be preferable to keep a world map icon nameless, but this isn't one of those instances.

For this level, you should add a bomb generator here:
If the player accidentally kills the bombs without blowing up the wall, then he/she is stuck here and has to exit from the episode.

That's not that good of a reward, especially considering there's only about three levels in between here and where the warp is leading. Instead, I suggest having the warp it leads to lead to a bonus level that can only be accessed by collecting all of the episode's stars. It would help to provide a use for the ones not needed to get to the final level.

Moving on:
You put a pipe up here, but it doesn't lead anywhere. I say replace it with a ? block or something.
I DON'T THINK YOU HAVE ENOUGH PARATROOPAS HERE FOR THE PLAYER TO AVOID. YOU SHOULD ADD, LIKE, TEN BILLION MORE TO MAKE THIS ANY SORT OF A CHALLENGE. Okay, seriously, you should remove some of those paratroopas and maybe use a variety of hazards, like the fire-plants or munchers or
anything besides this many paratroopas!

WHY IS TOAD PLAYABLE IF NOT ALL LEVELS CAN BE BEATEN AS HIM??

While I'm at it, WHY ARE THESE BLOCKS SLIPPERY??

World map suggestion #2: make sure that map icons actually lead to levels:
There may be an instance where it would be preferable to keep a world map icon levelless, but this isn't one of those instances.

I noticed something weird about this level:
The height of SMBX is 600 pixels, but the top of this section has been extended so that it is slightly higher (divisible by the standard block height of 32 pixels). Why?

World map tip #2:
If you have an icon warp to another place on the world map...

Make sure it actually warps on top of the corresponding icon rather than one unit beside it:

World map criticism #1:
These warps are completely pointless because it is simple enough to reach the "small island" by going through the levels normally.

All right, on to the final level:
You shouldn't use these airship NPCs here because they act like conveyor belts when bumping against blocks and, if I'm not mistaken, also consistently make an annoying sound effect while doing so(I'm not sure because my SMBX sometimes stops loading infrequently-played sound effects).

Some may call this mini-boss spam; I call it "easy."

Oh man; I didn't even have to fight the Boom-Booms! This was easier than I thought.

Hmmm...nope, still easy.

The text goes outside the boundary of the text box. This is rarely useful.

What? Could it be...? It is! It's funny! Only three problems: 1) I'm not Mario, 2) "Thanks" should be "Thank," and 3) The tree has some cut-off with the tree-boundaries inside the tree (I hope that made sense). Also, I'm not too fond of the use of "ermagerd," and I suggest it be removed entirely.

Wait a minute, that didn't do anything! What the heck?

I guess I should explain: when making an SMBX episode, it is customary to end the episode with an event that triggers the End Game drop-down "Bowser Defeat." This will play the SMB3 "Bowser Defeat" fanfare, and roll the pre-programmed SMBX credits. Some episodes, like The Apocalypse of Foroze and another one that I can't remember the name of, have the decency to build a custom credits-like level using sprite-swaps, layers, and events, but it is widely accepted for episodes to use the pre-programmed ending instead. Make a "Bowser Defeat" event (it only needs that End Game drop-down selected, it can otherwise be a blank event) and have it triggered by the star's death.
IN CONCLUSION:
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--The Tower of Bias
This is the forum's long running comedy series where people submit levels to a contest and complain about their placement when the scores are revealed.
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This is a collection of the absolute best episodes that have ever graced our community. You can tell that competition is tough because one of the featured episodes is just a cheap port of SMB3.
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-everyone
Oh, you wanted to know about your episode? Yeah, it's forgettable. I suggest experimenting with moving layers and sprite swaps so you can make your own boss instead of just using the ones pre-programmed in SMBX. Some good examples of custom bosses are the ones in
Mario Classic and the final boss in
Super Mario Quest Infinity. I also heard that there was a "custom boss competition" at some point; I can't seem to find it, though.