Papyrus very seriously considers it for a while. Of the three monsters, he has the most want to go home again someday. It's hard to admit he already knows the underground - or the surface - aren't home anymore, and that this carnival... is... for all that it's poorly rendered, Ringmaster what's with the blob mountains???

Anyway. He weighs the responsibilities he ran from and those he came here to fulfill (in different ways), those he's gained working in the carnival... and those he stands to gain, if he goes through with it. The notion of being one of the players on this stage of super powerful people, instead of just some mortal under another's protection... it's a lot. Not dying of old age someday is too, though it seemed like that was already the case so long as they stayed with the carnival...?

It's after hearing what his brother's doing that he decides for sure, as that's sorta the final factor; Papyrus doesn't want to die and leave his brother behind alone, after all. Not again.