[Question]
  [
This challenge is inspired by [@LuisMendo's MATL answer](https://codegolf.stackexchange.com/a/200008/75323) to my "[binary multiples](https://codegolf.stackexchange.com/a/200008/75323)" challenge.
# Task
Pick a [code-golf](/questions/tagged/code-golf "show questions tagged 'code-golf'") challenge that is *open* and that has been posted *before* this one; let me call it the *"linked challenge"*. The *linked challenge* must be a challenge whose task involves producing output.
Write the shortest code possible that satisfies the following restrictions:
* Your code must contain the characters `b`, `u` and `g` in your program, in this order and consecutively (case-insensitive, so "bug", "BUG", "Bug", "bUg", ... are all fair game.);
* Your code must *not* contain the letters `b`, `u` and `g` more than once (case-insensitive);
* Your code should be a valid submission for the *linked challenge*;
* When any subset of the (case-insensitive) characters `bug` are removed, your program no longer fulfils the task of the *linked challenge*. This may happen because your program now produces the wrong output (i.e. fails test cases), because it halted with an error, because it runs indefinitely and never returns (if this is the case, be prepared to prove your program runs indefinitely), etc.
* Your code should not be an integral copy - nor a trivial modification\* - of a submission that already exists in the *linked challenge* (for example, you may not copy [@LuisMendo's MATL answer](https://codegolf.stackexchange.com/a/200008/75323) to my "[binary multiples](https://codegolf.stackexchange.com/a/200008/75323)" challenge);
# Input
Your program takes input as per the specs of the *linked challenge* you choose.
# Output
Your program, in its correct state (i.e. with a bug\*\*), must abide by the output specs of the *linked challenge* you choose.
\* This is subjective so I appeal to your common sense; any imaginative modification should be fair game, even if in retrospective it is "trivial". This "no trivial modifications" rule will be "enforced" by me downvoting answers I think disrespect this...
\*\* Sit down, take a moment to let this sink in. Your program has a bug. And yet your program is correct.
# Posting an answer
When you post your answer, please provide a link to your *linked challenge*.
---
This is [code-golf](/questions/tagged/code-golf "show questions tagged 'code-golf'") so shortest submission in bytes, wins! If you liked this challenge, consider upvoting it! If you dislike this challenge, please give me your written feedback. Happy golfing!
  
[Answer]
# [Japt](https://github.com/ETHproductions/japt), 4 [bytes](https://en.wikipedia.org/wiki/ISO/IEC_8859-1)
Challenge: [Output with the same length as the code](https://codegolf.stackexchange.com/q/121056/84206)
```
BUG³
```
[Test it](https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QlVHsw)
## Explanation
`B`, `U`, and `G` are variables for 11, the input, and 16 respectively.
When applied to a number, `³` brings it to the third power.
In Japt, only the last expression is outputted, so only \$16^3 = 4096\$ is outputted, which is the same length as the code (4).
Since `B` and `U` are ignored, removing them have no effect on the output. However, their removal changes the length of the program, making it invalid. Removing `G` raises either the input (`U`) or 11 (`B`) to the third power. While \$11^3 = 1331\$ is 4 bytes, the program `B³` is only two bytes, making the output invalid. The variable `U` defaults to 0 when there is no input given, and \$0^3 = 0\$, which is only one byte long.
[Answer]
# Polyglot, 31 bytes
Linked challenge: [“Hello, World!”](https://codegolf.stackexchange.com/q/55422/58563)
This is a full program, as per the original challenge requirements.
```
print('Hello, World'+'bug!'[3])
```
[Try it in JavaScript (V8)!](https://tio.run/##y0osSyxOLsosKNEts/j/v6AoM69EQ90jNScnX0chPL8oJ0VdWz2pNF1RPdo4VvP/fwA)
[Try it in Python!](https://tio.run/##K6gsycjPM/7/v6AoM69EQ90jNScnX0chPL8oJ0VdWz2pNF1RPdo4VvP/fwA)
[Try it in Ruby!](https://tio.run/##KypNqvz/v6AoM69EQ90jNScnX0chPL8oJ0VdWz2pNF1RPdo4VvP/fwA) (thanks to [@Steffan](https://codegolf.stackexchange.com/users/92689/steffan) for pointing this out)
[Answer]
# JavaScript (ES7), 47 bytes
Linked challenge: [How many petals around the rose](https://codegolf.stackexchange.com/q/200386/58563)
```
a=>a.map(n=>t+=n**3&parseInt('bug',35)%9,t=0)|t
```
[Try it online!](https://tio.run/##XZFfS8MwFMXf@ynyok1nLetNGqaQiqDCcOAHKH2IsxvKTEdbB4Lfva4Njcc@9M@5Jzn53ZsPczLttnk/dte2fqv6ne6Nzk3yaY7c6ry70naxEJdH07TV2nY8fP3ah7HIooubuNPL6Kfrt7Vt60OVHOo9D4qiSGOWljFbnp9REApRusIoJDpZ6QqjUN4hTCNMI0wjTCNMI0wTLo0mQSiE3yPcj3eGNDUJ5R2JbBLZJLJJZJPIJpEtc2lyEoRCeILMVb0zpK0mobyjkE0hm0I2hWwK2dR8bjiGoQskHPpFf7hcTM78@pWfHAKKcX2KIxOz8@aDo9n@vyNS343D@NewGHfS6NHsztVUzdzbZZVBUp2q5pvzwsTMlhHTOdtxc/5qZqPgjoUvzyG7ZeHT/Xrz@BBG/S8 "JavaScript (Node.js) – Try It Online")
### How?
This is a port of [my Python answer](https://codegolf.stackexchange.com/a/200429/58563) to the linked challenge. This answer requires a bitwise AND with a constant, which happens to be \$6\$.
This \$6\$ is obtained with the cumbersome `parseInt('bug',35)%9` and removing any subset of characters from `bug` would produce a different (and therefore invalid) constant.
```
   s   | parseInt(s, 35) | mod 9
-------+-----------------+-------
 'bug' |      14541      |   6
 'ug'  |       1066      |   4
 'bg'  |        401      |   5
 'bu'  |        415      |   1
 'g'   |         16      |   7
 'b'   |         11      |   2
 'u'   |         30      |   3
 ''    |        NaN      |  NaN
```
[Answer]
# [C (gcc)](https://gcc.gnu.org/), 156 bytes
Answer to [99 bugs in the code](https://codegolf.stackexchange.com/questions/165623/99-bugs-in-the-code). Not competitive, but funny.
```
#define S"%d bugs in the code\n"
d;f(i){for(i=99;i;i=d)printf(S S"Take one down and patch it aro\x75nd\n"S"\n",i,i,d=(d=i+rand()%21-16)<0?0:d);printf(S,0);}
```
Also beats the C solution there.
[Try it online!](https://tio.run/##NYzNCsIwEITveYqlUkiwhVZQqbH4EPXYS8wm7SImpcYfKH32mIszMMxh5tPloHWMGzSWnIEuyxFur@EJ5CCMBrRH07uMobScxGL9zKltGkmSWhTTTC5Y3qXfVd0N@IRA/3GgHMKkgh6BAqjZ99/j3mECdVmKgpKx5djSdk5TLvJdXdYHca4u1QmF/HOLSsg1pg4PRY6/PaFgC4Mky4Vka/wB "C (gcc) – Try It Online")
[Answer]
# [Triangular](https://github.com/aaronryank/triangular), 6 bytes
Linked to Challenge: [Shortest code to produce infinite output](https://codegolf.stackexchange.com/questions/13152/shortest-code-to-produce-infinite-output)
```
bug>%<
```
[Try it online!](https://tio.run/##KynKTMxLL81JLPr/P6k03U7V5v9/AA "Triangular – Try It Online")
[Answer]
# [PHP](https://php.net/), 16 bytes
Solving [Output programming language name](https://codegolf.stackexchange.com/questions/107964/output-programming-language-name)
```
echo'2=7'^'bug';
```
[Try it online!](https://tio.run/##K8go@G9jXwAkU5Mz8tWNbM3V49STStPVrf/b2/0HAA "PHP – Try It Online")
Omitting any of the letters in `bug` outputs a wrong string. However, it won't cause any errors so that error messages containing `PHP` can never be outputted. All PHP answers in that challenge exploit either PHP flags, which cannot contain the word `bug`, or PHP errors, which omitting a letter from `bug` could still result in an output that fulfils the requirements.
[Answer]
# [Python 3](https://docs.python.org/3/), 24 bytes
```
while __debug__:print(1)
```
[Try it online!](https://tio.run/##K6gsycjPM/7/vzwjMydVIT4@JTWpND0@3qqgKDOvRMNQ8/9/AA "Python 3 – Try It Online")
*Linked challenge: [Shortest infinite loop producing output](https://codegolf.stackexchange.com/questions/13152/shortest-code-to-produce-infinite-output?noredirect=1&lq=1)*
Uses the fact pointed out by @Bubbler:
> 
> Python has a built-in constant called `__debug__` which is True by default. Removing some of its bug will obviously be an error. Though I can't find a suitable challenge for that...
> 
> 
> 
[Answer]
# [APL (Dyalog Extended)](https://github.com/abrudz/dyalog-apl-extended), 6 bytes
Solves [Output with the same length as the code](https://codegolf.stackexchange.com/q/121056/78410).
```
×'BUG'
```
[Try it online!](https://tio.run/##SyzI0U2pTMzJT9dNrShJzUtJTfn/qKO94P/h6epOoe7qIM7/AgA "APL (Dyalog Extended) – Try It Online")
Prints `1 1 1\n`, 6 bytes in total.
In regular APL, monadic `×` is Signum for numbers (-1 if negative, 1 if positive, 0 if zero). Extended provides an extended (no pun intended) definition for characters (-1 for lowercase, 1 for uppercase).
Because numeric arrays are printed with a space between items, deleting one char out of `BUG` will remove two bytes (`<space>1`) from the output, thus failing to solve the challenge. Deleting two chars will remove four output bytes, and deleting all of them gives only a single newline.
[Answer]
# [Zsh](https://www.zsh.org/)/[Bash](https://www.gnu.org/software/bash/)/others, 15 bytes
Challenge: [Output with same length as code](https://codegolf.stackexchange.com/questions/121056/output-with-the-same-length-as-the-code)
```
echo BUG{1..3}
```
[Try it online (Zsh)!](https://tio.run/##qyrO@P8/NTkjX8Ep1L3aUE/PuJbr/38A "Zsh – Try It Online")
[Try it online (Bash)!](https://tio.run/##S0oszvj/PzU5I1/BKdS92lBPz7iW6/9/AA "Bash – Try It Online")
[Answer]
# [CJam](https://sourceforge.net/p/cjam), 4 bytes
Challenge: [Output with the same length as the code](https://codegolf.stackexchange.com/questions/121056/output-with-the-same-length-as-the-code)
It's working. But I still didn't manage a 3-byte solution.
```
BUG^
```
[Try it online!](https://tio.run/##S85KzP3/3ynUPe7/fwA "CJam – Try It Online")
# Why it works
```
B    "Constant for 11";
 U   "Constant for 0";
  G  "Constant for 16";
   ^ "Bitwise XOR";
```
0 XOR 16 is 16, therefore it outputs `1116`.
# Removing a single character
```
UG^
```
It just outputs `16` without other calculations.
```
BG^
```
It outputs `27` because 11 XOR 16 is 27.
```
BU^
```
It outputs `11` because 11 XOR 0 is 0.
## Removing 2 characters
CJam doesn't have implicit input, so all these programs would throw an error.
[Answer]
# [Lua](https://www.lua.org/) and perhaps a polyglot in concept, ~~25~~ ~~28~~ 32 bytes
Along the lines of Arnauld's answer, linked to challenge [Output programming language name](https://codegolf.stackexchange.com/questions/107964/output-programming-language-name).
```
print('\076\117\097 5.'..#'bUg')
```
[Try it online!](https://tio.run/##yylN/P@/oCgzr0RDPcbA3CzG0NA8xsDSXMFUT11PT1k9KTRdXfP/fwA)
*Added 3 bytes Thanks to @RGS spotting the 'u' in 'Lua'*  
*Added 4 bytes Thanks to @MariaMiller for the 'L' and the 'a' as well*
[Answer]
[Create output twice the length of the code](https://codegolf.stackexchange.com/questions/59436/create-output-twice-the-length-of-the-code)
# [MathGolf](https://github.com/maxbergmark/mathgolf), 6 bytes
```
╘╘BUG]
```
[Try it online!](https://tio.run/##y00syUjPz0n7///R1BlA5BTqHvv/PwA "MathGolf – Try It Online")
[Answer]
# [C (gcc)](https://gcc.gnu.org/), 24 bytes
This one for real.
Answer to [Swap the parity](https://codegolf.stackexchange.com/questions/118819/swap-the-parity).
```
f(x){x=-(-x^!"bug"[3]);}
```
[Try it online!](https://tio.run/##XU7tasMwDPzvp7hlFOxW2dql@4C0fZEsg9RxUsPmDNsZYSHPntktlDL9OKST7nQybaWc54YPYhz2KU@Hj7vk2LdJkZUin@Z7beRnXyvsnK9193A6MKaNx1elDXjsKttKgjxVFstlGH4EGxlCxaVXzsvKKVeU2GPEhvBEyAhbwjPhhfBKeAvMJouwxZRftfrSNp0Nj4J6nUNjB@70r@oafrUWeMR/rliXQoT71UrgkibWtw2@DU8WNdIDFvW7Segmoi4Jtx46epzF0xmt8r01IQeb5j8 "C (gcc) – Try It Online")
[Answer]
# [C (gcc)](https://gcc.gnu.org/), 26 bytes
Answer to [Shortest code to produce infinite output](https://codegolf.stackexchange.com/questions/13152/shortest-code-to-produce-infinite-output)
```
f(){printf("bug"+2)&&f();}
```
[Try it online!](https://tio.run/##S9ZNT07@/z9NQ7O6oCgzryRNQympNF1J20hTTQ0oaF37HyiokJuYmadRlp@ZoslVzaUABCAprtr/AA "C (gcc) – Try It Online")
[Answer]
## Javascript, 8 characters
Linked question: [Output with the same length as the code](https://codegolf.stackexchange.com/questions/121056/output-with-the-same-length-as-the-code/121521#121521)
```
bug=>1e7
```
Outputs `10000000`, which has the same length as the program. Removing 1 or 2 characters would make it print the same thing, but wouldn't match the length of the program anymore. Removing all 3 is a syntax error.
[Answer]
# [05AB1E](https://github.com/Adriandmen/05AB1E), 4 bytes
Linked challenge: [Output with same length as the code](https://codegolf.stackexchange.com/q/121056/84206).
*Port of [Embodiment of Ignorance's Japt answer](https://codegolf.stackexchange.com/a/201227/6484).*
```
bugт
```
[Try it online!](https://tio.run/##yy9OTMpM/f8/qTT9YtP//wA "05AB1E – Try It Online")
[Answer]
# [Jelly](https://github.com/DennisMitchell/jelly), 8 bytes
**[Reverse Bit Order of 32-bit Integers](https://codegolf.stackexchange.com/questions/36213/reverse-bit-order-of-32-bit-integers)**
```
%Ø%BUGƇḄ
```
[Try it online!](https://tio.run/##y0rNyan8/1/18AxVp1D3Y@0Pd7T8//9f19LCxMLAyNLADAA "Jelly – Try It Online")
I managed to find a challenge that actually uses two of the letters in a productive way.
There's no Jelly answer to the challenge at the time of writing this answer.
## Explanation
```
%Ø%BUGƇḄ Main monadic link
%        Modulo
 Ø%        2^32
   B     Convert to binary
    U    Reverse
      Ƈ  Filter by
     G   Format as a grid
       Ḅ Convert from binary
```
[Answer]
# [Ruby](https://www.ruby-lang.org/), 24 bytes
Linked to [Find the number of integers in the range from 1 to N that ends with 2](https://codegolf.stackexchange.com/questions/200363/find-the-number-of-integers-in-the-range-from-1-to-n-that-ends-with-2)
```
->n{(n+5+"bug".size)/10}
```
[Try it online!](https://tio.run/##KypNqvyfZvtf1y6vWiNP21RbKak0XUmvOLMqVVPf0KD2v7GpXklmbmqxQkq@Qk1mDZeCQkFpSbGCknJ1Zq2CcnWankamZq0SV2peyn8A "Ruby – Try It Online")
[Answer]
Linked to challenge: [Find the number of integers in the range from 1 to N that ends with 2](https://codegolf.stackexchange.com/q/200363/9481)
# [Python 2](https://docs.python.org/2/), ~~95~~ \$\cdots\$ ~~39~~ 35 bytes
Saved a byte (in a previous version) thanks to [Maria Miller](https://codegolf.stackexchange.com/users/92689/maria-miller)!!!  
Saved a byte (in an other previous version) thanks to [Surculose Sputum](https://codegolf.stackexchange.com/users/92237/surculose-sputum)!!! 
```
def f(n):print((n+len("bug")+5)/10)
```
[Try it online!](https://tio.run/##Hcs7DoAgDADQ3VM0TG0Y/IWF22ik2MQUQnDw9NW4veXVp59FF7MjMTAqxdpEO6L6Kym6/c6OfKBxnsi4NBAQhbZpTrgGigPAH0A@MQrZCw "Python 2 – Try It Online")
[Answer]
Linked to challenge: [Find the number of integers in the range from 1 to N that ends with 2](https://codegolf.stackexchange.com/q/200363/9481)
# [C (gcc)](https://gcc.gnu.org/), ~~51~~ ~~42~~ 40 bytes
```
i;f(n){for(i=0;n+=2,"bug"[i++];);n/=10;}
```
[Try it online!](https://tio.run/##HcrNCoMwDADge58iFISEVKYbO2X1RZwHrVRyWByyncRn736uH1@ql5RKUclotOd1Q42NGMdz8NN78b0yD0Jip9g2cpTHqIa0u/@0F/y23i5XYVZyAM/tqxl9NUPdQTXfzQcNkFGJxB3lAw "C (gcc) – Try It Online")
[Answer]
# [JavaScript (Node.js)](https://nodejs.org), 39 bytes
Linked Challenge: [How many petals around the rose](https://codegolf.stackexchange.com/questions/200386/how-many-petals-around-the-rose)
```
a=>a.map(n=>t+=n**3&!!'bug'[2]*6,t=0)|t
```
[Try it online!](https://tio.run/##XZFfS8MwFMXf@ymyF9PWWtabNAwhFUEFUfADlDzE2Q1lpmOrA8HvXteGxmMf@ufck5z87s2HPdnj@vC@765c@9b0G91bXdn80@5jp6vuUrs0FReLBX/92vKaTKqyTi@Tn65ft@7Y7pp8127jqK7rImOFydjy/IyCUAjjC6OQ6JTGF0ahgkOYRphGmEaYRphGmCZ8Gk2CUIiwR/if4AxpahIqOBLZJLJJZJPIJpFNIlvp0@QkCIUIBKWvBmdIW01CBUchm0I2hWwK2RSyqfnccAxDF0g49Iv@cLmYXIb1qzA5BBTj@gJHJmbnzQdHs/1/RxShG4/xr2Ex7qTRo9mdq6la@rfPMlHenJrDdxzXNmPOJExXbBPb81czl0Q3jL88cXbN@MPt4/P9HU/6Xw "JavaScript (Node.js) – Try It Online")
Originally posted as [a golf to Arnauld's answer](https://codegolf.stackexchange.com/questions/201217/ah-why-is-there-a-bug-in-my-program/201218?noredirect=1#comment478744_201218).
[Answer]
# [W](https://github.com/A-ee/w), 6 [bytes](https://github.com/A-ee/w/wiki/Code-Page)
Challenge: [Output the same length as code](https://codegolf.stackexchange.com/questions/121056/output-with-the-same-length-as-the-code)
```
BUG"2*
```
Repeats the string "BUG" multiple times.
[Answer]
# [Python 2](https://docs.python.org/2/), 13 bytes
Solves [Output with the same length as the code](https://codegolf.stackexchange.com/q/121056/78410).
```
print 'bug'*4
```
[Try it online!](https://tio.run/##K6gsycjPM/r/v6AoM69EQT2pNF1dy@T/fwA "Python 2 – Try It Online")
Prints `bugbugbugbug\n`.
---
# [Python 2](https://docs.python.org/2/), 27 bytes
Solves [Hello, World!](https://codegolf.stackexchange.com/q/55422/78410)
```
print'bugHello, World!'[3:]
```
[Try it online!](https://tio.run/##K6gsycjPM/r/v6AoM69EPak03SM1JydfRyE8vygnRVE92tgq9v9/AA "Python 2 – Try It Online")
Removing some of `bug` will chop off characters from the beginning of `'Hello, World!'`.
[Answer]
# [J](http://jsoftware.com/), 7 bytes
Solves [I double the source, you double the output!](https://codegolf.stackexchange.com/q/132558/78410)
```
>:Debug
```
[Try it online!](https://tio.run/##y/qvpKegnqZga6WgrqNgoGAFxLp6Cs5BPm7/7axcUpNK0/9r/k8DAA "J – Try It Online") [Try it online!Try it online!](https://tio.run/##y/qvpKegnqZga6WgrqNgoGAFxLp6Cs5BPm7/7axcUpNK06HUf83/aQA)
Prints 1 as given, 2 doubled.
### How it works
Monadic `>:` is "increment" (add 1), dyadic `>:` is "greater or equal" (`x >= y`).
```
>:Debug    NB. increment 0; gives 1
>:Debug>:Debug
  Debug>:Debug    NB. 0 >= 0; gives 1
>:                NB. increment it; gives 2
```
---
# [J](http://jsoftware.com/), 12 bytes
Solves [Output with the same length as code](https://codegolf.stackexchange.com/q/121056/78410).
```
echo 6#Debug
```
[Try it online!](https://tio.run/##y/r/PzU5I1/BTNklNak0/f9/AA "J – Try It Online")
Somewhat similar to Python, J has a stdlib variable `Debug` which is initialized to the number 0. `6#` replicates the zero 6 times, and `echo` prints it. The output formatting is identical to APL's (space-separated numbers), so the output is `0 0 0 0 0 0\n`.
Being a terse language, I suspect there could be a more suitable challenge for J which gives a shorter solution using `Debug`.
[Answer]
# [Io](http://iolanguage.org/), 18 bytes
Challenge: [Output programming language name](https://codegolf.stackexchange.com/questions/107964/output-programming-language-name/108201#108201)
(Joke ruiner over here, never mind.)
This errors (outputting the language name) when the bug is inside, and it doesn't error when any part of the bug is removed.
If you think that this uses the `i` character (taken from the question):
> 
> Note that this is case sensitive. I can still use the char 'b' because it's different from 'B'.
> 
> 
> 
```
if("bug"size>2,iO)
```
[Try it online!](https://tio.run/##y8z//z8zTUMpqTRdqTizKtXOSCfTX/P/fwA)
## Explanation
```
        size       // Is the length of
   "bug"           // the string "bug"
            >2     // larger than 2?
if(           ,    // If so,
               iO  // Access an undefined variable
                 ) // Otherwise, do nothing
```
# [Io](http://iolanguage.org/), 19 bytes
Challenge: [Output with the same length as the code](https://codegolf.stackexchange.com/questions/121056/output-with-the-same-length-as-the-code)
```
"bug"at(2)cos print
```
[Try it online!](https://tio.run/##y8z//18pqTRdKbFEw0gzOb9YoaAoM6/k/38A "Io – Try It Online")
# Explanation
```
"bug"               // The sequence "bug"
     at(2)          // The 3rd index of that
                    // (Out-of-bounds indexing returns nil)
                    // This returns an integer for an in-bound index
          cos       // Find the cosine of that
                    // (Cosine over nil throws an error)
              print // Print that value to STDOUT. (WITHOUT a newline)
```
# [Io](http://iolanguage.org/), 19 bytes
Challenge:[Shortest infinite loop producing no output](https://codegolf.stackexchange.com/questions/59347/shortest-infinite-loop-producing-no-output)
```
while("bug"at(2),0)
```
[Try it online!](https://tio.run/##y8z//788IzMnVUMpqTRdKbFEw0hTx0Dz/38A "Io – Try It Online")
# Explanation
```
      "bug"         // Base string "Bug"
           at(2)    // Try to access the 3rd item of the string
                    // (Out-of-bounds returns nil)
while(          ,   // While that's true:
                    // (So a string is always true and nil is always false)
                 0) // No action needed
```
[Answer]
# Java 8, ~~88~~ 87 bytes
Linked challenge: [Is this number a prime?](https://codegolf.stackexchange.com/questions/57617/is-this-number-a-prime)  
Given a number, outputs truthy/falsey depending on whether it is a prime number.
```
n->{int i="BUG".charAt(2)-70;for(;n%++i%n>0;);System.console().printf("%s",""+(n==i));}
```
[Try it online](https://tio.run/##XZBPa8IwGMbvfoqHQCGhWusug2UVtsvYYe7gdho7xDTOuPqmNNExpJ@9S7VMMIeE98@TH8@zVQc12Zbfna6U93hRlo4jwFIwzVppg0VfAgdnS2ge@yAhY6sdxcsHFazGAoQC0@ny1wezy7Qj7yrDBTbKY2UMoTF1FX8r8WPDBsOe24cxvKVIuUisB7kAv69r14SocIS359eOJvNjT7cFe3x/YpneqOYh8Bsxuc3l2jVcUpKmNqF5LoW8ELK6ibI1Z4lnY8ZSTkVhhZBtJ3sH9X5VRQeDkZPLXcyAL0OUfX18QolzAD3izJ9J2PtilufxTdNhDFwjuU3ZHdgprP5QFuP7r663K@LDrD2F23Z/) (Note: `System.console()` is `System.out` on TIO, since TIO doesn't support console).
**Explanation:**
```
n->{                // Method with integer parameter and no return-type
  int i=            //  Integer `i`, starting at:
    "BUG".charAt(3) //  Get the third character from String `"BUG"` as unicode value
     -70;           //  and subtract 70 from it, so it'll become 1
  for(;n%++i        //  Increase `i` by 1 first before every iteration with `++i`
            %n>0;); //  And loop as long as `n` modulo-`i` is not 0
                    //  NOTE: The second `%n` is to stop the loop for input n=1
  System.console().printf("%s",
                    //  Print to STDOUT with String format:
    ""+(            //   Convert the following boolean to String:
        n==i));}    //   Check if `n` and `i` are equal
```
Prime checker credit goes to [*@SaraJ*'s answer here](https://codegolf.stackexchange.com/a/181611/52210), which is rather ingenious.
Things I had to do to comply to the challenge:
1. The challenge description mentions program (and technically the linked challenge as well), but this isn't possible in Java. I know [five different ways](https://pastebin.com/55PUYiXs) of creating a full program in Java, but each of them requires at least one of the letters `bgu`. Usually I can get past source-restrictions by using `\u`-unicode escapes, but since `u` is one of the restricted characters that's also not an option here. Luckily OP allowed functions as well, which is (much) shorter anyway.
2. I couldn't use `return` since it contains an `u`. And I also couldn't use `System.out.print(...)`, since it contains an `u` as well. So instead, I use [`System.console().printf("format",...)`](https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/Console.html#printf(java.lang.String,java.lang.Object...))
3. Since I wanted to print a boolean, the format to use in the `printf` would be `"%b"`. Unfortunately, `b` is blocked, so instead I use `"%s"` and convert the boolean to a string.
4. And last thing to tackle was of course sneaking `bug` in, so it works with it, but doesn't work anymore without it. I've done this by changing the `int i=1;` to `int i="BUG".charAt(2)-31;`, which grabs the third character in the String (the `'G'`) as unicode value (`71`), and subtracts 70 from it to make it `1`. If any of the `B`, `U`, and/or `G` is removed, the `.charAt(2)` will fail with a `StringIndexOutOfBoundsException`.
[Answer]
# [R](https://www.r-project.org/), 15 bytes
Linked challenge: [Output with the same length as the code](https://codegolf.stackexchange.com/questions/121056/output-with-the-same-length-as-the-code)
```
strrep("bug",5)
```
[Try it online!](https://tio.run/##K/r/v7ikqCi1QEMpqTRdScdU8/9/AA "R – Try It Online")
(or [18 bytes](https://tio.run/##K/r/v7ikqCi1QEMpqTRdT09PScdI8/9/AA) if we include the default `[1] ""` formatting with which [R](https://www.r-project.org/) surrounds its ouput, but this restriction did not seem to be applied to the original linked challenge).
[Answer]
# Batch, 11 bytes
Linked challenge: [Output with the same length as the code](https://codegolf.stackexchange.com/questions/121056/output-with-the-same-length-as-the-code)
```
@echo %bug%
```
Outputs `ECHO is on.` when run regularly or when some of `bug` is removed, and outputs `%` when all of `bug` is removed.
[Answer]
## Javascript (82 characters)
Linked challenge: [Integer lists of Noah](https://codegolf.stackexchange.com/questions/187879/integer-lists-of-noah)
```
c=>eval('O\x62ject').keys(x={},c.map(a=>x[a]=(x[a]||0)+1)).some(z=>x[z]!=2)&&'bug'
```
It's a bit lame, but I'm defining my outputs as producing 'bug' when input list is not a Noah list, and `false` when it is.
I love this challenge though. Maybe I can find a better solution. :)
[Answer]
# TI-Basic, 6 bytes
Linked challenge: [Output with the same length as the code](https://codegolf.stackexchange.com/questions/121056/output-with-the-same-length-as-the-code)
```
BUG
ᴇ5
```
]