You had invited both Sans and Papyrus to a show Nasptabot allowed you to do, you even told Sans to wear his old blue armor. Just to make the surprise better.

"Are they here yet?" You asked Undyne, Undyne nodded and handed you the mic, you ran onto the stage in your usual black hoodie with gold sneakers and arm socks. "HEEEELLO YOU DEADLY MONSTERS! TONIGHT WE HAVE A SPECIAL SHOW FOR THE ROYAL GUARD SANS AND HIS BROTHER PAPYRUS! ENJOY!" Nasptabot announced, the music started to play.

I was only walking through your neighborhood

Saw you loud honey in the cold I stood.

Anywhere I go there you are.
Anywhere I go there you are.

I been getting used to waking up with you

I been used to waking up here

Anywhere I go there you are
Anywhere I go there you are

There you are
There you are

You're the fire and the flood
And I always feel you in my blood
Everything is fine when your head is resting next to mine
Next to mine.
You're the fire and the flood.

AWOOOOO!

Monsters started to dance as you danced on the stage, Sans and Papyrus were even bobbing their skulls to the music.

Since we met I started to feel a lightness in my step

You're miles away but I still feel you

Anywhere I go there you are
Anywhere I go there you are

Late at night when you can't fall asleep

I'll be lying right beside you, counting sheep

Anywhere I go there you are
Anywhere I go there you are

There you are

You noticed Papyrus and Sans smiling as you sung, you swirled and pointed to them.

There you are

YOU'RE the fire and the flood
And I always feel you in my blood
Everything is fine when your head is resting next to mine

Next to mine

You're the fire and the flood

AWOOOO!

Again you danced on stage but, Sans and Papyrus joined in. Both were smiling and having a good time.

Each took turns dancing with you, leaving you laughing and enjoying yourself like the old days.

Now listen here she said
Boy when you know you'll know
And I know

You're the fire and the flood
And I always feel you in my blood
Everything is fine when your head us resting next to mine
Next to mine

You're the fire and the flood

Sans and Papyrus hugged you as you finished the last note, leaving you giggling and hugging them back around their necks.

"What did I tell you about wearing blue?"

"VERY GOOD CHOICE (Y/N)."

"*Yeah, you're our night."