Digging into the "Gift of the Little People" folktale type (ATU 503), where someone joins the singing of fairies and gets rewarded for it. The human usually adds a few days to the song of "Monday, Tuesday, Wednesday!", delighting the fairies.
Hungarian versions, once again, have to be extra about it.
Instead of singing fairies, we have singing skeletons. And they get angry when someone adds "Monday" to their song.
Highly relatable.