Sans blushed a little as Frisk flicked the stray noodle away, chuckling,"Hey now, maybe I was savin' that for later. Never question a skeleton's motives." 

He took another bite, watching as Frisk wiped her mouth on the back of her hand. Paps would shit bricks if he had seen that. And then he would have blamed Sans for encouraging such slobbish behavior. Honestly, it was relaxing to see someone else forgoing proper table etiquette, seeing as he didn't have an ounce of it in his bones.

As far back as he could remember, he'd always taught Papy to use his manners, showed him how to care for himself, and had one day been intending to leave his younger brother in search of.... Someone he could hardly remember. But be it Sans just being careless, or Paps intuition, the younger knew he would leave one day and had begged him not to. Of course Sans would never have said no to him, even without the begging, but seeing Papyrus so broken and disheveled at the mere thought of him leaving... Sans knew he could never leave Pap alone.

They needed each other too much.

While Sans was strong and fully capable of protecting them, Papyrus was his foundation. His little brother kept him sane, comforted him when he couldn't ask for it, and made life fun.

Paps was his comfort zone.

Speaking of which, Sans wondered when his brother would be back.

Surely before dark, right? For Mettaton's sake, the robot had better hope so. It wouldn't be pretty if Paps came home with a cold or "accidentally" spent the night there. Sans decided he'd call his brother later to check up on him.

In an effort to distract himself, Sans began to slurp his noodles loudly(how that was even possible without lips was a mystery in itself), slurping louder with each mouthful.

He glanced at Frisk playfully as he slurped a particularly loud noodle, grinning ear to ear at the silent challenge he'd issued. Hey, since it was just them in the house, why not have some fun with it?

He sat back in his chair, taking a few gulps of his ketchup as he waited for her to either accept or ignore the challenge.