Now please allow me to get to my original point!

This Sans would happen to not come from any specific universe but be literally an error!

Each universe would contain that 'summoning box' below it!

Opening it up would be inviting it into the universe and thus causing it's destruction!

It doesn't have any legs, it's body can transform into anything so it manifests as anything while still always resembling Sans one way or another!

You could say it is merely an illusion and nothing real!

I know that it may look as if I just got lazy and didn't want to do a proper body, I'm sorry! Thank you!
But the truth is that this is just what I saw fitting, I apologize! Though thank you!

From the bottom of my heart, I am so very sorry for taking up your precious time! Thank you for reading this!