DID NO ONE KNOW THAT UNDYNE DOESN'T LIKE PAPYRUS'S BROTHER??
She dislikes him in a way it's not obvious, I only noticed it by chance (after reading the phone calls yet again). I tried looking it up and haven't found anyone talking about it so hm hm.
WELL THEN LET ME DROP SOMETHING IMPORTANT!
Papyrus doesn't lie to Undyne about liking grease because he's trying to get her approval (if he did, he wouldn't be teasing her the way he does in later calls), he is lying to her BECAUSE HIS BROTHER LOVES GREASE.
Instead of saying "WOWIE!! MY BROTHER LOVES GREASE TOO!" He tells Undyne that HE also loves grease, because he knows that Undyne doesn't like his brother, and the last thing she would want is having something in common with him.
I know there's people that believe Papyrus is too stupid or self absorbed (He isn't) to notice or know things like this about other people but Papyrus's care for others and caring about their likes and dislikes is shown very clearly right in Snowdin forest (In the murder route cough cough).
Edit: Forgot to add important context: Both Flowey and Undyne treat Papyrus's brother the exact same way
-They talk about him poorly when they DO speak about him. -They never directly use his name, and only refer to him as "Papyrus's brother' -Undyne refuses to speak to him, or around him, she stops speaking in phone calls after Papyrus's brother has
