Asgore is only getting teeth so it doesn't count, he's probably getting it from Toriel.

Papyrus is known to be silly so this isn't out of character.

Asriel is known to be dramatic due to the trauma of his backstory, so this is normal.

Sans is rarely out of character, so it's him.

"Kris get the bannana" is a line from Deltarune, Deltarune has Susie in it, Susie is pixelated, Sans is pixelated.

That's rotten, when you die you become rotten, when people are dead for long enough they are skeletons, skeletons are made out of calcium, Sans is calcium.

what's it being made in? Is it in flash or flip-a-clip?

So Alphys Z is an edgy undead version Alphys that likes Sans instead?