If you type %15 in your search bar you will find this weird symbol “”.

This symbol breaks Scratch in a lot of ways.
If you name a sprite with this symbol, your category bar will partially vanish entirely.
Or if you make a variable with “” symbol, it'll seem like it's invinsible, but if you click on other sprite or scene and go back, all script will be gone…

These are some examples of what can “” symbol can do.

Scratch on!

You can also put it in sounds, costumes, etc.

You can even remove inputs using it…

when I recieve {:: events reporter } :: control hat

By the way i know what this “square thing” is. It's the negative acknowledge character (U+0015) which is why the glitch is the %15 glitch. In the Google URL bar, when you type a specific Unicode character it says %(2 lengthed unicode holder) so that's why it is the %15 glitch.

The reason why this “square thing” is a “square thing” is because the font that Scratch uses is Helvetica Neue, and that font doesn't have the U+0015 character, and the placeholder if the letter/character is not included is a square box.

Why does it entirely break Scratch?
Well, I don't know but…

Negative acknowledge is an explicit character used to send a protocol to the server and sometimes the NAK(abbreviation) breaks the server and it causes some assets to glitch out like how if you name a sound “” it removes all blocks that are not in the first 3 rows which do not glitch out.

In the variables if you name a variable “” the variable control assets glitch out and hide themselves and not work, and doing the trick where you go to another sprite and come back, the block system completely freaks out and erases both sprites' code that you used for this trick.

Why does it remove inputs?
Typing the NAK character in one of Scratch's block text boxes and reloading the sprite's code (costumes and back to code) removes an input and deletes some blocks. Now when the code reloads, Scratch's BTB system glitches out and converts the first BTB into a block untypable box (BUB).

What is the deal with this red hacked block?
Scratch's CB (custom block) system breaks and doesn't load but instead loads a red hat block which you absolutely cannot connect a block to.

If you rename one of your sprite costume, all of the sprite code box except motion and looks hides. Fixes if you remove the  symbol from the name

but how do you copy it?

@HarryCreator2416

red hat

oh wait no It didn't work

oh I did it

define 
stop [HAHAHAHAHA v]

 hmm

%15

my favorite glitch is: 

The square glitch works from %10-%19. I messed around with the numbers, and apparently %41-%79 slaps a letter on the search bar.
%65: E
%20-29 leaves a leaves some symbols.
%30-39 might leave some punctuation.

king of the page no edit

can reproduce
My browser / operating system: Linux, Firefox 132.0, Flash 32.0 (release 0)