I credit you, @C_A_T_D_E_C_K! Sans had finally had it with the look on the kid's face. With that look, it told him they had k!lled him 392 times. So, he decided to not hold back. But he sent so many attacks, the game crashed, with a Blue Screen showing up. Somehow, this made Sans realize: HE WAS IN A GAME. This made him go mad, and k!ll everyone in Undertale, and fuse with the Blue Screen. To this day...he t0rtures EVERYONE in his game. He IS Undertale.
Sans: * allagameallagameallagameallagameallagame... AU by me!
