Sans has the energy of an isekai protagonist. He's not even from Undertale. He's literally just a guy surrounded by mystery forced upon him
Hes trying so hard to keep up with everything going on by gathering as much intel as possible because he's still adjusting to this new and strange universe. He even studied quantum physics because of course its a real thing here.
Like. Imagine how he feels.
He wakes up one day in undertale and after a costume party, his brother wants to join the guard. A real guard. As in. There's a kingdom. In real life. A millenia old goat with a blood red trident is the king. Who personally trained a bloodthirsty fish lady who is the captain. Somehow his brother befriended her. They're making spaghetti. He also got Sans a job as a sentry through her.
She's in love with the royal scientist who frankensteined a bunch of monsters on the verge of death by using the mysterious properties of human souls. She's also the most normal out of everyone in this bizarre modern medieval cave. Most of her equipment is stuff she gathered from a dumpster.
That scientist made a living robot. Who is also the head of a major fashion brand and a TV star. His brother is all about his brand. Their burgers are made of sequins.
His brother has also befriended a talking flower. He's been making research with the royal scientist about timeline stuff because he's trying to find a way back home and that flower is a prime suspect.
His brother one day comes in with a lot of premonitions. Sans doesn't know if it's because of the flower or if he just woke up like that.
They have a dog now. It's vibrating and it teleports at random. His brother says it won't leave him alone. He has a feeling that it's somewhat divine. Papyrus dodges all of his questions by jumping out of a window. The window glass scatters inwards.
And then he meets a human. They're probably just as lost and confused as him, right?
Wrong. The human can bend time and space and has death defying stubbornness. Monsters are weak to intent. That human could singlehandedly eradicate all of them.
Even the lady behind the door is strange. She's the queen and lost her children in a tragedy. And now her children are haunting the narrative.
Is it really that weird then that he spends most of his time at Grillby's?