The grin that lights up Sans' skull as Neil speaks is a sickly and twisted thing. He dissolves into what might become apparent after a moment is equally hysterical laughter along with his fellow sceintist. Is he okay? Neil, more than anyone, should know what happened to him.

But even that bitter resignation fades into shock when Ryoji speaks. Sans' head snaps up, his eyelights flickering with shock. Thanatos? The human who helped Mettaton run the party was the masked, winged monster who smashed up the castle? How did he change back? How did he change in the first place?

Everything still hurts, but that thread of hope is enough to let Sans carry on speaking, sounding a little more coherent or at least a little more aware.

"I...I can't change back. Not alone." OR at least, he couldn't last time. Sans shakes his head frantically, only to stumble a step away from them with a pained yelp as his skull cracks again, growing just a bit more angular and bestial. His voice, when he speaks again, is undercut with a low whine of pain. It hurts to focus, but no moreso than everything else hurts right now. "I, I-I don't know how. No Gaster. No pods. No lab." He wasn't exactly in a position to notice how his brother fixed him last time.