Regardless of Sans' more solid form now, Asriel really is heavier. Not by too much, thankfully. He's still a kid. But Sans can tell it's going to take a little more effort to get him up, even as Asriel loses is balance.

"Whoah, whoah, whoah."

The former skeleton kneels down properly now, taking Asriel's arm and side so the small monster can lean against him.

"Don't worry about it. I'm still gettin' used to my body too. Ready?"

One hand moves to Asriel's back, and the other - hesistantly - under his tail.