This is the "sans." replacement
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DIALOGUE:
OH.
YOU ARE... NOT WHO I THOUGHT YOU WERE.
NEVERTHELESS, HELLO, HUMAN! I AM THE GREAT PAPYRUS.
WELCOME TO SNOWDIN! (AND THE UNDERGROUND TOO, I GUESS.)
HAVE YOU SEEN MY LAZYBONES BROTHER, SANS, ANYWHERE? HE SAID HE'D BE HERE EARLIER...

OH, THERE HE IS.
QUICK, HIDE BEHIND THAT LAMP BEFORE HE GETS OVER HERE.
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Please ask permission before using this song, I worked hard to make it.
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LEITMOTIFS:
Nyeh Heh Heh! (Modified)
Bonetrousle
"Nyeh Heh Heh!" but from a parallel universe
Bonetussles
Megalo Strike Back
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Undertale by Toby Fox
Undertale: Opposite Day by CloudMouth27
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ABOUT THIS AU:

"Undertale: Opposite Day" is my take of Underswap that changes some of the swaps while keeping major parts of the original characters' personalities

Major Swaps (both ways):
Sans <--> Papyrus
Undyne <--> Alphys
Toriel <--> Asgore
Napstablook <--> Mettaton
Asriel <--> Chara
Riverperson <--> Gaster

Frisk is replaced by a human named Uri, and Flowey is replaced by a Doll that Asgore knitted for Chara named Dolly.
Gaster exists again and he's the Royal Scientist whilst Undyne is his apprentice instead of Alphys.
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EXTRAS:
Papyrus wears actual knight armor instead of his regular Battle Body

Papyrus is now the Older Brother

When Duty Calls!

(* Uri enters the Balcony of the Nightclub and sees Papyrus playing a guitar while sitting on the corner railing)

P: Oh! Hello, Uri.
P: What A Pleasant Surprise.
P: Is It Too Loud In There?
U: Yeah, it is.
P: ...
P: Why Don't You Sit With Me For A Bit? You Must Be Exhausted From Walking Everywhere.
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This is the "It's Raining Somewhere Else" replacement
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If you want to use this song, then please ask permission first and credit me. I worked hard to make this and don't want it to go to waste.
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LEITMOTIFS:
Dating Start (Modified)
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Undertale by Toby Fox
Undertale: Opposite Day by CloudMouth27
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ABOUT THIS AU:

"Undertale: Opposite Day" is my take on Underswap that changes some of the swaps while keeping major parts of the original characters' personalities

Major Swaps (both ways):
Sans <- -> Papyrus
Undyne <- -> Alphys
Toriel <- -> Asgore
Napstablook <- -> Mettaton
Asriel <- -> Chara
Riverperson <- -> Gaster & Flowey
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Papyrus is playing a guitar in this scene and that's why the only instrument is an acoustic guitar :3

Under The Weather

“Undertale: Opposite Day” is an alternative take on Underswap that changes some of the role swaps while keeping major parts of their original characters’ personalities and changing the minor parts of them to fit their new roles.

Locations:

Ruins → Wilted Gardens
Snowdin → Thistlebrook Swamp
Waterfall → Shardsong Depths
Hotland → Coremaris
New Home → Daylight Hollow

Role Swaps:

Toriel <- -> Asgore
Sans <- -> Alphys
Papyrus <- -> Undyne
Napstablook & Mad Dummy -> Mettaton
The Fun Gang -> Mad Dummy
Frisk → Asriel -> Chara
Gaster <- -> Gerson
Riverperson -> Flowey
Snowdrake -> Noelle Holiday
Chilldrake -> Dess Holiday
Snowdrake's Mom (Crystal) -> Rudolph Holiday
Snowdrake’s Dad -> Carol Holiday

This track is not available anymore.

Other tracks from UNDERTALE: OPPOSITE DAY (Cloud's Underswap)