I wonder if Sadnesses count as being carbon/water-based lifeforms? ...Or even count as being "alive"? Because, like... they're formed from strong emotions, but don't necessarily need tears for their creation... just because they could assumedly be labelled as "parasitic" in needing to "feed" on something carbon/water based to exist doesn't mean they themselves need any of that after being "born"...
All I'm saying is that if Ryland Grace's homesickness ever reached the point of accidentally spawning Mal du Pays (who I think would still look like Siffrin, since they would presumably be the "origin point" for that specific "subspecies" of Sadness), he'd probably immediately have a field day trying to study it. ...If it didn't manage to freeze him first.
Assuming it even bothered with that and didn't just stare at him creepily from a corner or something.
...On a similar note, I wonder if Loop counts as carbon/water-based... it is still unclear whether or not they still count as human (or whatever species the people of the ISAT world would be considered in this crossover, since the existence and ability to utilize crafts probably means they and Earth humans don't count as the same species) or are just a being totally comprised of Wish craft, so...
Though I bet Grace could totally still see colors in the ISAT world beyond red, since the game makes a point that they do still exist there, it is just that people lost the ability to see them. Which would be another fascinating foray into the different senses shared by different species.