A skymaid is a cloud-sky being, and is the "afterlife" or "next stage" of a mermaid.The heart of a mermaid has to be stolen, which K'nuckles does, after evading the mermen guarding her, deciding this is ok because "Mermaids are weird". Mermaids are then gradually killed when people use the wishes, called "mermaid tears" in their hearts (which is actually a bowl). These tears are little candies carried in a golden glass case shaped like a heart and the have the power to grant any wish, with no limitation it's assumed. Breathing syrup, floating on clouds, teleportation, knowledge, and changes to physical appearance are a few of the wishes granted to Flapjack and K'nuckles.
The skymaid encourages Flapjack to always keep wishing, since wishes bring about the mermaid's transition into a skymaid. She tells him in a friendly tone that if he keeps wishing all his dreams will come true--but, when answering Flapjack's question "Even the scary ones?" she laughs and answers (in a very low, nightmarish, masculine voice) "Yes." The skymaid is good-natured has a sense of humor, as she told K'nuckles a hat and a corn-dog, things he wished for with the last two wishes but in one sentence, are two things as an aside as she left. Captain K'Nnuckles incorrectly reiterates his opinion that mermaids are weird.