i could see papyrus getting rightfully upset with sans if he were to find out that he lies to him about a lot of things. papyrus is already aware that sans hides stuff from him but not quite the extent of it. and i get the feeling sans is hiding some really important stuff from his bro.
oh, that could certainly be true. i subscribe to the idea that papyrus knows WAY more than he’s letting on though, so that post was mostly written with that in mind lol. still, in that situation i think papyrus would overall be more upset about everything sans is hiding rather than being upset with sans himself. papyrus believes in everyone unconditionally and it’s not without reason—he might be naive and unaware at times, but there are certain levels where he understands people extraordinarily well.
it’s often to a fault. papyrus seems to know when people are lying to him, but he goes with it anyway, probably just to keep them happy. he cares deeply about the friends he has, and he recognizes his capability to make people happy. to most, he’s just a goofy, naive, shenanigan-loving skeleton; the idea that someone so carefree and innocent could exist in such a cruel world is inspiring to them, so they try to shield him from that cruelty. i think papyrus recognizes that—really, i think he prefers embodying that idea. just like sans, papyrus wants to keep going for the sake of the people around him.
the king papyrus ending shows this better than anything else:
IT'S STRANGE.
ASGORE, ALPHYS, METTATON, AND UNDYNE WENT AWAY.
SANS SAYS THEY WENT ON VACATION.
and then later, once sans is gone,
he’s pretty blatantly lying to himself here, unless anyone wants to tell me that papyrus is completely unaware of the concept of death? (which, no.) papyrus seems to outright refuse to acknowledge the bad things in his life, probably to cope with them—sans, meanwhile, is acknowledging them constantly, and can’t stop it. both extremely unhealthy!
so if he found out sans was intentionally trying to hide things from him—important things—i think he’d empathize with why, even if he’s upset with his dishonesty. whether or not he’s right for doing so, sans is hiding them because he doesn’t want anyone else to have to deal with the exact things that hurt him. papyrus would be completely right to be upset about this, but i don’t think he would be—papyrus knows why people lie to him. he’d probably be much more upset that his brother was suffering alone.
