Couldn't find a picture, but I'll try to draw GB! Error! Sans at some point. Also, Blueberry is going to be included in this as well. No regrets. :3
Requested by lokiplayz
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Error sighed as he looked through the codes of a random au out of boredom. Being stuck in the antivoid really did get boring after awhile. He rested his chin on his hand, wishing that something exciting would happen for once.
"Are you okay?"
Error turned to look at Blue. He chuckled as he walked over towards the captive skeleton.
"Y'know, I've looked through these codes so many times I can't even count. I am bored out of my mind. So you tell me if I'm okay," Error growled.
Blue didn't respond. He looked away sheepishly.
"That's what I thought," Error grumbled, turning away from Blue.
"So which au are you looking at now?" Blue asked.
"Gaster Blaster. It's a very... interesting one, to say the least," Error replied.
"What's the 'head canon', or whatever you call it?"
"It's mainly one about Sans, but it occasionally includes Papyrus or even Gaster. Basically, Sans can transform into a gaster blaster. You know what those are, right?" Error explained.
"Umm, yeah. Me and my bro both have those. I don't use them as much though," Blue responded.
"Well, he turns into one of those. Almost like a werewolf of sorts," Error chuckled to himself.
"Does it... hurt him at all?"
"Depends. Most people have it canon that the transformation does hurt him. Heh, fucking sadists. People are so obsessed with pain and torture these days," Error mumbled.
He winced slightly, though whether it was the thought of such a painful transformation or from the building pain in his chest, he was not entirely sure.
"You okay?" Blue asked.
"Yeah. Totally fine. Just thinking about how much that would hurt. I almost feel sorry for him, but it ain't my problem," Error lied.
At this point, he was certain that it wasn't just the thought anymore. He could feel the pain building within him. But he tried his best to hide his pain from Blue. The last thing he needed was for Blue to see him suffering.
He gritted his teeth, trying to avoid eye contact with Blue.
"You don't look so good..." Blue murmured.
"I'm fine! Stop worrying about me!" Error snapped, his voice becoming slightly more glitched than usual.
Blue flinched.
Error sighed. "Sorry... I'm not sure what's wrong with me right now. Eh, it's probably just the boredom starting to get to me."
Blue looked worried, but said nothing. The two skeletons avoided eye contact for a few moments. Eventually, Error collapsed to the ground as the pain in his chest became unbearable. Blue's attention snapped back to the other skeleton, a concerned gleam in his cyan-colored eyes.
"Error?"
Error clutched a hand to his skull as he grunted in pain. He curled up into a ball, covering his face with his arms. Blue tilted his head to the side in confusion.
"What the... Why does it hurt?" Error mumbled.
"What do you mean? What's wrong?" Blue asked.
Error didn't reply. He pulled his hood over his head, trying to keep his face hidden from Blue. He trembled, his body temporarily becoming more glitched than usual.
Error felt like he was about to be ripped apart. Blue kept trying to talk to him, but Error was barely listening. A loud static had filled his skull, making it hard to hear the other skeleton.
That was when he looked down at his hand. He realized that the tips of his fingers had grown sharper.
   "Huh?! Why is this happening?!"
   Blue's cyan-colored eyes flooded with concern. "What's going on?!"
   "I didn't think... How is this au affecting me?!" Error exclaimed.
   "What do you mean?"
   Error was about to respond, but before he could say anything, a sharp pain through his spine stopped him. He barely held back a scream at the sudden pain.
   "Error, please! Answer me!"
   "I... can't..." Error cut off with a glitched scream.
   Blue flinched as he heard the sound of bones cracking. The sound was somewhat drowned out by the glitched sounds that usually accompanied Error's presence, but it was undoubtably there.
   Spikes began to emerge along the glitched skeleton's spine. Error groaned in agony, his voice glitching. He dragged his newly-formed claws along the ground, gritting his teeth as pain overtook him once more.
   Blue could hardly tell what was happening to the other skeleton due to the excessive amount of glitches surrounding him.
   Error tried to stand, but fell back down as his feet began to change, the tips of his toes growing into sharp claws as another wave of pain was sent through him.
   Blue watched in horror as the familiar skeleton in front of him rapidly transformed into a large, glitched skeletal beast. He tried to back away, but he was held back by the blue strings that had kept him captive in the first place.
   The beast crept closer, his tail flicking. He opened his mouth, blue strings trailing from his maw as he began to charge up a ball of magic, aiming it towards the captive skeleton that cowered below him.
   "Please... Don't hurt me..." Blue murmured.
   The beast released a huge beam of energy from his mouth, the attack barely missing Blue. It instead hit the strings that held Blue in place. The strings snapped, allowing Blue to escape.
   He darted between the beast's legs, making a mad dash for the portal back to his home universe. The beast roared as his captive escaped.

A/N: Sorry this one took so long! My phone shattered and I couldn't update for a few days. Plus I was at a loss for words for a while on this. :/

I'll try to update as soon as I can, since I have several requests that I can work on. ;3
-Sora