Theories/predictions - Marceline
Theory
In the episode 'Take Her Back', Marceline had two dreams of in which both of them she has grown 'old and withered'. The first dream of her visiting Betty and Simon while they bake a pie and Marceline appears older, as if she has biologically grown. Also in her second dream, during her 'poison coma' she has clearly aged significantly and has trouble hearing. These dreams may be foreshadowing an upcoming death for Marceline. This is also further proved at the beginning of the poison coma dream where Peppermint Butler is seen digging a grave, portraying his knowledge of Marceline's impending death. Death may come to Marceline through her somehow being able to age normally and she would pass of old age, as suggested through her dreams. I…