Thesis: the real reason we act like people who want to get railed by Sans from Undertale are so much weirder than people who want to get railed by Undyne isn’t because being into a skeleton is objectively any stranger than being into a fish – it’s really just because Undyne is tall and Sans is short.
People in the notes are like “no, it’s because Undyne is buff and and has big boobs” – really?
Her sprite is pencil-necked, narrow-hipped, and flat as a board. Sure, she’s got some pretty ripped biceps, but that’s all she’s got – to all in-game evidence, she’s got a build like if the Once-ler showed up for arm day and only for arm day.
If you’re willing to look at that and imagine Undyne as jacked and stacked, but you’re not willing to picture Sans with a bangin’ dad bod, that’s on you.