"Okay, so i’ve always had this theory that the Ghost lady is actually fionna from the f&c episodes. Simon met her before his travels with Marceline. Fionna would travel down into the hyooman bunkers and bring them food and supplies. Fionan died in a Lubbglub attack though, which is why we saw a skull with her hat on it. after she died she didn’t go to the dead world though, she stayed in ooo. she came to her old home (the mansion fro, the creeps) So anyways that’s why ice king says ‘i know you’re out there’ in his dreams to fionna but not to cake. he made up cake and PG and marshal to fit the story."