I don't own Underswap or Undertale. Neither do I own the Gaster Blaster Sans AU. Hope you like it anyway! ^^

Chapter 3: The Blue Glow

(Papyrus POV)

I walked to Muffets, in the cold and in grief that I hadn't watched Sans closer. Maybe I can rethink my thoughts on where he might be over some honey and a cigarette. Yeah, that'd be nice. I got to the door and walked inside. The place was full like always and went up and sat at the bar. I didn't bother to look around. It's not like he is here anyway. Muffet spotted me and came over to me.
"I'll have the usual," I said.
"Hey, I've been waiting for you! How could you leave your brother like that?!"
I looked up at her confused, "What'd do you mean?"
"Sans, does that ring a bell in your lazy brain?"
"Sans is here?!"
"Yeah, he was wearing your jacket, he's in the back. Come on." She opened the door on the side of the bar. I got up and followed her to the back door, where she led me into the kitchen and food closet. It was a mess. I was surprised at first since I knew she was very tighty and liked things organized. I looked at Muffet. Her expression was surprised as well, she had probably not made that mess. Huh this place now kinda reminds me of my bedroom when Sans or Dad doesn't try to clean it, now that I think about it.
"I just cleaned this yesterday!" Muffet scowled at no one while still looking at the mess.
"Where is Sans?" I asked trying to get the point why she dragged me back here. "Cause he's not here."
"He was! I took him back here not to long ago. Did he cause this mess?"
"I dunno. He is usually really organized, but hyper when he eats sweets-…you didn't give him sweets did you?"
"It was only a small lollipop!"
"That explains it. This is why we don't give him sugar. The last time he ate something sweet, he was still a baby bones and just learning how to walk, I think I was like 12 or 13, I don't remember. Dad came home from work that night and bought us nice cream. I was fine when I ate it, but Sans was all over the place, jumping and running around, even if he tripped and fell at some points. His eyes even glowed to show how much energy he felt. It was around midnight when he finally burned out all the energy and we were able to put him to sleep. That's when Dad decided not to give him sweets anymore. That was back before, when Sans could glow both of his eyes."
"What do you mean both of his eyes?"
"Well Sans' right eye is broken. He can still see out of it, but he can't glow his eyes with that pupil anymore."
"What happened?" Muffet sounded more concerned now. She can be really attached with children so I dunno if that's just how older girls respond when they see little kids, or it's just Muffet being Muffet.
So I continued anyway. "Well when Sans was about 1-" *CRASH!* We both jumped at the loud noise. We rushed that way, behind the stoves, there he was. There was flour everywhere on the floor, and in the middle of it, sat Sans. A bucket that had the label 'Flour' on it was on top of Sans' head, practically covering his face and head. He was wearing his usual clothes, with my spare, now-flour-covered, orange, jacket. A muffled giggle could, be heard from under the bucket. I walked over and pulled the bucket off his face. Sans smiled up at me, happily. He was also glowing his left eye, blue. That part saddened me since, it was a while since I'd seen Sans' eye glow his blue colored magic, mine is an orange glow by the way.
Sans giggled, "Papyrus!" And he gave me a big hug. I smiled and hugged him back.
"P-Papyrus….," Muffet whispered, in a some what scared/in horror tone. What got her so scared all the sudden? I let go of the hug to look at her.
"What?" I asked her casually. Her face expression was in horror as she starred at…Sans?
"L-Look…," she pointed at Sans with one of her hands. I turned to look at Sans. Then I saw what she meant.

(Sans POV)

I felt so happy an hyper after I ate that lollipop. I felt as energy rushed through me. I ran around the place after Muffet told be to stay back here, I may have made a bit of mess running around and crashing into stuff. That's when I heard Paps' voice. I got excited and bumped into a shelf. Next thing I know, a bucket of flour falls on me with a crash. I hear footsteps rushing my way and someone removes the bucket off my head, revealed to be Papyrus. I gave him a hug and then Muffet starred at me in shock for some reason. That's when I noticed I was getting some kind of headache. The back of my head and my teeth hurt like fire. Papyrus pulled me out of the hug and starred at me with shock and concern. My body started heating up with pain. Everything hurt, mostly my spine, legs, hands, and head.
"P-Papyrus…wh-why does e-everything hurt…?" I tried asking my big brother through the pain. I looked down at my hands, with look of shock, I saw that I had claws for fingernails. My hands were also flaming blue. I started to cry and panic. What was going on?! Papyrus only starred at me in shock and horror. What's wrong with me?! The pain continued for what felt like half and hour and Papyrus did nothing but but his hands on my shoulders. During that time, I felt and heard bones cracking and snapping. What was happening to me?! The pain finally stopped after some time and I fell and layed down on the floor, my hands covering my face which was pouring with tears. My body was sore and shaking like crazy. I was so scared. I felt Papyrus pick me up and pull me into a hug. I clung my arms around him, not wanting to let go. I couldn't move. I didn't want to move. Why…? Is this why Dad said not to go outside, because he knew this would happen? I should have listened then! I'm so stupid! I started crying in Papyrus's jacket (the one he was wearing). Papyrus rubbed my back and trying to soothe me I guess.
As he passed Muffet, he said, "I gotta get him to Dad…" I fell asleep in Papyrus's arms after that. The pain was too much to keep my eyes open.

Poor Blueberry, but I hope u guys like the story so far!