Sans had noticed Papyrus's odd behavior, he'd been acting weird for a month now, ever since the costume party he'd been excited for. Sans had noticed the way Papyrus came home that night, showering and then locking himself in his room until morning. Sans comes home from Grillby's a fresh new ketchup stain on his shirt. "Hey, Pap, I'm back," He calls out, hand in his jacket pocket.