Sans is a MONSTER and not a HUMAN, so he doesn't follow HUMAN biology like a HUMAN skeleton. Same with Gaster and Papyrus.    

--------------------------------------------------------------

On the way back to their old home, it was probably no surprise that Sans had fallen asleep, even if like the last time, he had wanted to try and force himself to stay awake so he was prepared for anything, in case anything happened. But honestly, being a monster who was soul pregnant, it was pretty exhausting; not only was he looking after himself, but a little life that was developing inside his soul. With a soft smile, Frisk happily allowed the skeleton to softly snore away, with his head rested on her shoulder. Any moment that she could get him to rest, she would gladly take it, just because him sleeping during the day was something that he didn't enjoy doing, and she could sense that. 

This was likely because of the fact he had worked in the Mafia since he was 17, so if he had the time to sit around and be lazy, she would have been pretty surprised. Whether he was a lazy, laid back person before he joined the Mafia, she had absolutely no idea. She just knew he refused to sleep in the day time, (if he had a say in it, and their little one didn't force him to sleep by exhausting him). And being part of the Mafia, when you were doing things, you were pretty damn active; you had to stay active to even be fit enough to do missions, so laziness was likely a far away concept to this skeleton boyfriend of hers.

"You guys might want to duck down for now." Mettaton suggested, seeing as they were getting closer to their destination, and it wasn't like he had tinted windows to stop people from seeing them on the outside of their car. "At least until it's definite we're in the clear." Mettaton went on, causing Frisk and Papyrus to nod, and they both carefully unbuckled their seatbelts. 

Carefully going to lift Sans' skull off of her shoulder, Frisk decided that she would hide the both of them by laying down across the back seats, allowing Sans to use her as a pillow as he continued to sleep; thankfully she hadn't woken him up in the process of fussing around, trying to hide them from sight. Papyrus just tried to duck down in his front passenger seat, and wanting to hide him better, Mettaton decided to take off the black blazer he was wearing to throw it on top of Papyrus. "I hope you aren't afraid of the dark." Mettaton teased, hearing a small laugh from Papyrus at that comment while he continued to drive.

Having no idea how much time passed, the human girl just stared at the ceiling of the car, holding Sans close as she softly stroked the back of his skull in a soothing manor, wanting him to continue sleeping peacefully as they travelled. After some silence that had felt like it dragged on for eternity, they finally heard Mettaton say: "Okay, it's fine to get out now." He promised, actually already going to get out of the car himself. Hearing this, the human went to gently shake Sans awake, hearing him stir and grumble a little as she did.

"Sans, we're here. It's time to wake up." Frisk softly spoke, causing the monster that was laying on top of her to slowly blink his eyes open, seeming confused for a moment, likely because he probably realised he had changed position from where he had last been before he had fallen asleep. "We had to hide, so I let you rest on me as your pillow." Frisk joked, causing Sans to blink at her, before he started to slightly blush and grumble in embarrassment. 

"geez, ya could have just woke me up..." He replied, going to climb off of her and sit up properly, while she giggled slightly, saying that that wouldn't have been an option. She had wanted him to rest, so she had allowed him to continue to sleep. It was difficult not to roll his eyes at such a thing, but even after rolling his eyes he still said: "well... thanks..." He muttered with a weak smile, before going to climb out of his side of the car, with Frisk and Papyrus also getting out of the car themselves.

"we should probably get out of the open pretty quickly. i don't want anyone seein' us." Sans mentioned almost the moment they had gotten out of the car. "speakin' of which, mettaton, ya probably should have parked somewhere else, not right outside." Sans went on as they went down the dodgy looking alley way that Frisk would never forget as the same alley way she had been so nervous about on day one, when she thought it looked like a good place to get murdered. Now it was just some area they walked through to get where they went to, and it was completely normal to her now.

"Well, Undyne does not suspect me. Even if she found my car parked around the area, I don't think she would get the idea to come here." Mettaton pointed out. "I know what I am doing." The robot added, considering he had so far done a better job of not getting found out for being a spy than anyone else had -- no offence to his darling Papyrus of course. But he had no plans to get discovered, and being someone who had been created by Alphys, it was a lot easier for the robot to scoot past those gills of hers unnoticed.

"if ya say so..." Sans sighed, as they entered through the front door to Grillby's bar, which surprisingly had a few customers sitting around at tables who were clearly just minding their own business, not really caring about them entering. For a minute, Grillby looked ready behind his bar to greet them with a smile, but that smile quickly transitioned into a look of complete and utter shock as if he hadn't seen the faces that had greeted him in years.

"Sans, Papyrus, Frisk!" Grillby exclaimed from where he was standing. (only not exclaiming Mettaton's name in surprise, as he had seen him enough times as of recently to not be thrown through a loop at his presence).  "What are you guys doing here?" He questioned, as they walked closer enough to not be shouting at each other across the room. "I heard the news about you and Sans." The flame monster pointed to the human and the shorter skeleton. "Congrats by the way." 

"uh, thanks. do ya know where dad is? we need to talk to him." Sans mentioned in a serious tone, wanting to make this whole thing quick and snappy just to get it out of the way. Yes, he had missed seeing Grillby and if he felt like he had the patience, his greeting to him might have been less impatient and more friendly, but he just wanted to talk to his father about what him and Frisk were worried about. 

"AS YOU CAN TELL, IT'S SORT OF SERIOUS." Papyrus decided to speak up, hoping to be of aid to his restless brother, who did actually give him a somewhat thankful look for trying to back him up into quickly wanting to find Gaster. Grillby blinked at them, questioning if everything was okay, which only caused Frisk to butt in and say everything was fine, just that they needed to have a serious discussion with him. 

"He's probably down in his lab working on something. I know he'll be happy to see you guys, he has been missing you a lot." Grillby smiled, glad that them showing up would likely cheer the oldest skeleton up who had been missing the two members of his family that had gone away for awhile. The flame monster could never blame him for being a little disheartened over it, knowing they were his own children and that the bond he had with them must have been special that long distance from them felt terrible. 

"i'm sure ya have been keepin' him happy though. he likes ya after all." Sans pointed out, earning a small chuckle and slight blush from the flame monster, before Sans already wanted to start stepping towards the elevator. As he did, Mettaton mentioned how he would just stay up here at the bar, while they ventured down to see Gaster. While he was interested in Sans' condition, at the same time he didn't want to stand around and listen to all that science mumbo-jumbo. 

Stepping into the elevator, Sans suddenly found himself feeling extremely anxious, and upon seeming to notice this, Frisk went to gently grip onto his hand, giving it a small squeeze, while Papyrus put a reassuring hand on his shoulder and he gave him a friendly brotherly smile. These two just always showed him that he was never alone in his truest moments of need, and he was so glad that he had them when he actually felt... Scared for what he might be told. He didn't want to be told that there was a high chance he would die during the birth of their child, or that they would die. He just wanted everything to turn out okay.

He wouldn't be sure what to think if things didn't.