Story (In Real Life)
The user of Lucario the Skeleton had a dream. It was about a supposed "Undertale 2" It was like Undertale, but it spanned across several different AUs. And the games main mechanic was being able to edit the game files in game. While he was dreaming himself playing the game, he had the feeling to do something a bit sadistic during a genocide route.
Before he started the route,he wanted to delete Underswap Papyrus from the games files, so there would be no one to stop him from completing the route. He open the files and deleted the entire folder containing Papyrus's code. Lucario kept playing, but he found Papyrus in the usual spot he would stand in. His sprite was glitchy, and had blue boxes all around him. When Lucario spoke to him, Papyrus said the same dialogue he would in that spot, but the text bio repeated words, and blue boxes covered most of the words. The sprite of papyrus's head was glitchy with whited out eyes.
After this was the tile puzzle room. Underswap Sans was standing next to Papyrus looking completely unaware of what has happen to him. Papyrus began to speak, (which was strange since Sans was the one who's dialogue was scripted next.) And Papyrus only said: bad time, over and over again. While he said it his text box glitched out more and the screen began to glitch and shake. The entire game crashed and instead of kicking Lucario out of the game, (In much the same fashion Flowey does before his Omega battle) The game kicked him out of the dream itself, and he woke up in real life.
Story (In Game)
Crashed!Swap!Papyrus looks the same as his Swap! counter part, but has turned glitchy and has strange, blue boxes around him. His eyes have been whited out, and a secret message inside the eyes can be seen if you zoom into his eyes and look at your screen the same way that makes the colors look semi-negative.