My top 10 versions of Gaster's Theme. 
Note that despite Soundcloud's numbering system, the #10 pick is actually the one below the original, and the #1 pick is at the bottom. That way it functions like a countdown.

Some rules apply as always:
1. The song has to be for an AU.
2. Covers and takes are allowed, remixes are not.
3. Only one entry per AU. For example, a song and a cover of that same song or alternate version for the same AU could not both be there.
4. Any variations of "!Underswap" (or !Underfell or whatever) all count as the base AU (i.e. Underswap). (Something like Integrity or Undertale: Swapped, however, could coexist on the list)

Slick's Top 10 AU Gaster's Themes

* nyeh heh heh! the old telescope trick!
* it's so funny.
* pardon me, where are my manners?
* the name's paps.
* short for papyrus.
* i'm pretty great.
* my brother though?
* the best.
* he's got a knack for hunting down humans such as yourself.
* in fact, i think that's him over there.
* quick, come on through this gate.
* my bro forgot to add a password to the switch to open it.

((Papyrus Design by Ghost, https://bsky.app/profile/sleepingghost.bsky.social))
((Papyrus Sprite by Orbyy, https://twitter.com/OrbyyNew))
((Thumbnail done by ThatJan, https://bsky.app/profile/thatjan.bsky.social))

paps!

sans 3
this one kind of sucks but i dont really care too much

MEGALOVANIA - Legacy Arrangement

cover by https://soundcloud.com/totallyautumn (formerly known as DJT0B3, DJTOB3 and Tabitha)

Original Description:

loved the original and really wanted to cover it. i tried to make this sound more like that creepy slowed down version of anticipation in genocide and i think it turned out pretty cool.

original track by https://soundcloud.com/shipel and https://soundcloud.com/malk-mald-bhb
check it out and the cool storyswap take it's from HERE! --> https://soundcloud.com/storyswap-project/24-last-goodbye
idk who made the sprite but if you did lmk so i can credit you

...

audio source: soundcloud
original artist nickname: tabitha💕
original dead link: https://soundcloud.com/tabitha-official/last-goodbye-cover
release date: wasn't saved (except year)
long-term storage: possible, no obstacles for now. The song's artist is aware of this reupload.

[Storyswap] Last Goodbye (Cover) ✧ Re-up

-
BATTLE START!
-

＊┈┈┈┈＊┈┈┈┈＊┈┈┈┈＊┈┈┈┈＊

Track composed by :
SynthMint’s

Discord server:
https://discord.gg/Kb8cMTZCGY

10. Approaching Foe

-
As she guides you through these flourishing sights amidst the purple walls of violet, the old Lady sparks a conversation.
-

* You see, young one.
* Even far away from home, I assure you will be safe.
* The people that inhabit these walls alongside myself are sure to welcome you with open arms.
* They are as curious about you as you are of them. And I understand that all that curiosity might be overwhelming. 
* But rest assured that they mean no harm. They are merely just interested in learning more about you.
* You will be fine. 
* ...
* ...
* ...
* But maybe... Maybe I might be wrong.
* Maybe it is for the best for you to have a learning experience.
* To know what to do if you encounter someone that wants to push the limits.
* Someone like... whatever foul creature left you so harmed.
* Someone... someone like...
* **Them**.
* Yes. I made up my mind. You must learn.
* Learn for your own safety.
* It's for the best, my dear.

- 
By the time she finishes her monologue, you two are far deeper down the catacombs. She seems to be looking for something.

Her attention turns to one of the pillars in the room. There appears to be something laying behind it. She goes out to grab it, and sure enough - it turned out to be a training dummy! (well, it's more of an abandoned mannequin than a dummy, but it's the spirit that counts!).

She puts down the worn-out model right up next to you, then instructs what you must do as she heads to the other side of the room to watch.
-

* Think of this as a threat. Someone that wants you hurt, or even worse.
* What would you do in a situation like this, young one.
* Please show me you're capable of fending off against them.

-

*  You engage the training dummy.

♡ * Dummy

♡ * Check
* Talk
* Flirt

* DUMMY - OFFENSE 0, DEFENSE 0
* A button eye and a cotton cheek.
* Makes a face that leaves all meek.

* Check
* Talk
♡ * Flirt

* You wink at the dummy.
* ...
* As a dummy, it does not have a mouth to reciprocate.
* No one's happy about this.

＊┈┈┈┈＊┈┈┈┈＊┈┈┈┈＊┈┈┈┈＊

Track composed by :
SynthMint’s

Discord server:
https://discord.gg/Kb8cMTZCGY

11. A Completely Harmless Opponent!

* Smells like a rotting, slimy, fly-ridden vegetable.

♡ * Toader
* Decayoid
* Moldred

♡ * Mystify
* Compliment 

* (You hold your hands out in front of you!)

* (You cover your thumb and… detach it off your hand!)

* (Toader seems unimpressed)

♡~~~~~~~~~~~♡

* Green is poisonous! Take down this food pyramid! With love~

* Ribbit, ribbit!

* (Human, why do silly parlor tricks when this world is so beautiful!)

* Burble Burrrrb!

♡~~~~~~~~~~~♡
…..

♡ * ( You take out a spoon…. wait, where did you get that?)

* (You hold out your spoon and miraculously bend it with little effort!)

* (Toader seems shocked by this!)
* (Toader has been snapped from their delusions)

* Ribbit! 
(Wait, human, what have we been doing?)

* I get all the nutrients I need from the ceiling lights! 

* Burb Burble?

♡~~~~~~~~~~~♡

…..

* (You complimented Toader)
* (Toader really didn't understand what you said but seemed happy anyway!)

* Eat greens… NO! ONLY WHEN I DIE!

* Burble Burb.

* Ribbit Ribbit (Happy!) :>

♡ Spare

♡ * Toader
* Decayoid
* Moldred

＊┈┈┈┈＊┈┈┈┈＊┈┈┈┈＊┈┈┈┈＊

Track composed by :
SynthMint’s

Discord server:
https://discord.gg/Kb8cMTZCGY

12. Enemies Close to Home

discord.gg/U9qFw8yUdV
↑my discord server
original @thedrop0ff
thumbnail by @morimoto0507

Sound Of Silence (2025)

i am so original
yes its a brazilian meme i thought it was funny ok
megalovania by toby radiation fox
inspired by https://soundcloud.com/sea_slug megalovania https://soundcloud.com/sea_slug/megalovarnia

makitalovania

From Now On | ONYX BLASTED

FRIEND INSIDE ME

One of the songs that play in the Sound Test room.

Toby Fox - UNDERTALE Soundtrack - Unused: Gaster's Theme

Megalos overrated.

I decided to fuck around with Harmor after watching some tutorials and I ended up making this.

Original art in the cover by @kompletekrysys

EDIT: Here's an invite for the HD server
https://discord.gg/Pe6qrvs

[Undertale AU - Harmonic Dysfunctions] The Unknown (Updated)

[Disneytale] The Mad Doctor

*̡͡ ͞S̷̡̧a͢v̶e̴͡ ̧o̢͟n̢ ͏̢ȩv͢͝͡e͏҉̡r̴͝y̛͠t̶̶h͟ì͏n͜g͜͠ ̸in͢ ͜҉Ć̷h̀͡r̡̀i͏́s̕҉t́m̀͏̕a͞s̨͠ ̸͠i̧͘͜n ̕[͏̷͝R̶E̕͟DA̧͝C͏̨ŢĘ̷D̡҉].̴

[Terrible Choices AU] - The Forgotten Month

Track made by @thetunehero-956661993
thumbnail also by @thetunehero-956661993

join the server!
https://discord.gg/37AubMj

{MultiVersal Mistake} Ost: ???

Hysteric Hangout

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