Game crash when feeding Pig King with Halloween decorators

If it's of any help it seems only to happen when using custom characters giving pig king any item, at least on my end.

Yeah, same here. It's not any particular mod doing it, it's only with (most) mod characters. And that strikes me as odd, since this same exact thing happened last year, but it only happened with a particular character mod enabled on the server and would happen on any character at all as long as it was. I know it's an issue only happening with mods, but I still hope Klei does something about it nonetheless. I really want to get those special skins by actually playing, and doing so with all my usual mods and stuff.

Already reported, and it is as you suspect- modded characters are the cause.