Marceline/Analysis of Marceline's origin

Facts
"Memory of a Memory" shows Marceline aging over time. During a period which is presumably during or shortly after the Mushroom War she is shown as a young girl. Later, during the incident where her father ate her fries, she appears to be in her teens. In the scenes where she is with Ash she appears to be closer to her current age.

Young Marceline has the same pale skin, pointy ears and fangs that she has as a teenager or adult. However, little Marceline hops through trees instead of floating over them, appears outside in the daytime without protection, and has no bite mark on her neck. The older Marceline during the fry incident also does not have a bite mark. The mark only appears on her neck when her memories of Ash begin.

According to Natasha Allegri, she was not bitten when she was 16 or 17.

According to Pendleton Ward, Marceline was probably a vampire before the apocalypse.

In "Return to the Nightosphere," pictures on the walls of Hunson Abadeer's house show Marceline with her father at the same age as the earliest memory of her in a post-apocalyptic city. Whether this is a result of bad parenting, her running away, or her actual heritage being questionable, we do not know. However, it is likely that for some reason at that point her parents were out of the picture due to unexplained circumstances.

According to the episode, "I Remember You," she met the Ice King as Simon Petrikov. It is also revealed that he gave her Hambo. She looks a few years younger than her youngest appearance in "Memory of a Memory".

In "Finn the Human," we see a universe where events transpired differently, and Marceline is never bitten, and appears physically very old. She still refers to her age as 1000. Also, in this episode, she refers to herself as "a half demon" instead of a vampire.

Source of Marceline's physical traits
Marceline's pale bluish skin, ears and fangs are all similar to those of her father and could have been genetically inherited from him. According to writer Adam Muto, Marceline's father is more of a demonic creature than a vampire. In the episode Daddy's Little Monster there are many paintings, in one of them it shows young Marceline with Hunson Abadeer and an unidentified woman, who could be her mother. In another painting he's holding Marceline as a baby.

Marceline appears to prefer clothing and hairstyles from the 1970's through the 1990's the most. This may be the time frame that she grew up in as an adolescent/teenager/young woman, or she may just like the fashions and hairstyles from those eras.

It is possible that Marceline is a vampire human and demon. She stated that she was half demon in "Finn the Human" so her extra powers might be a result of this (like her ability to change into various monster forms including bats, wolves and tentacle beasts), so she could possibly have become a vampire in the first memory and used special powers to age more.

There is a possibility she was born a humanoid with vampire-like features and got bitten turning her into a vampire. It is possible that not all vampires have all her abilities, it could be that powers she has that traditional vampires don't have (e.g. levitation) could be inherited from her father. Another possibility is that she was turned into a vampire at the age of 18 or so, after the fries incident, giving her immortality and her current powers.

It is unclear when Marceline became a vampire or how Marceline is able to age over time, since typical depictions of vampires have them remain frozen at the age they are bitten, and are only able to reverse the appearance of time, to give the appearance of looking younger, instead of progressing in age to become older in appearance. Character designer Andy Ristaino has stated she is "kinda a shape shifter" though, so this could explain her growth.

Fries
In the "fries" memory, the teenage Marceline wanted to eat fries, something that vampires presumably would not be interested in, since they mainly consume blood and shades of red, but it could also have been for the ketchup.

In "Henchman," Marceline says that she "kinda likes" the pain she feels when she's in sunlight because it reminds her of when she would scrape her knees when she was a kid and her mom would "patch her up." This both confirms she actually has/had a mother, and points out there might be a possibility that she feels love or some type affection towards her mother.? It's probably because her mother is human and not immortal that she wasn't with Marceline during the war.In "Memory of a Memory" and "I Remember You" she is shown, as a child, outside and not being burned by the sun. Being able to move about without protection could be explained by a large quantity of fallout in the atmosphere, which could have blocked out a large amount of the ultra violet rays. This is supported by the burning city viewable in the back ground.

Marceline's Age
Marceline has commented several times that she is "over a thousand years old," which makes one think, based upon Memory of a Memory, that the Mushroom War occurred around a thousand years ago. One could argue that Marceline could be fibbing about her true age. However, based upon the evidence regarding the Ice King and his origin as revealed in Holly Jolly Secrets Part Two, Marceline seems to be telling the truth about her age.

In the episode, the Ice King is revealed to have been a human living in civilization before the discovery of the Ice Crown, which mutated him into his current supernatural state. As previously revealed by Pen Ward, the Ice King is at least 1,000 years old, which means that humans and civilization were in existence around 1,000 years prior to the start of the series, to the point that national cultures and boundaries still existed (with him mentioning he found the crown in "Scandinavia," which is an actual location on modern Earth). Marceline's Closet revealed that she has kept a journal for at least 500 years that she was going to write into a song, but Marceline merely said she had "500 years worth," proving that she could have worked on the journal even longer and just wanted to write the song based on 500 years worth of material.

From this, a few possibilities seem to exist regarding Marceline's age and, likewise, the time of the Mushroom War and it's aftermath:

statement that Marceline was probaly a vampire before the war.
 * The first is that the War did occur a thousand years prior, and that the Ice King is older than the 600 previously mentioned, closer to Marceline's age which, as stated, is at least 1000. It is shown in I Remember You that Ice King is older than Marceline because when he finds her she looks to be around 4 or 5 and he is in the final stages of his transformation into the Ice King. This would most likely mean he found the crown before Marceline's first flashback, because he lived in civilization pre-war and Marceline was first seen during/after the war. This was later confirmed by Pen Ward when he revealed that the Ice King is 1,000+ years old, maybe even a little older than Marceline.
 * Another possibility is that Marceline is lying about her age. As known, Marceline fibs about things all the time to make herself greater than she is, such as riding on giant goldfish in the middle of the daytime. Thus, she may be lying about her age to make herself look greater.
 * Another possibility is that Marceline's mother was a vampire, causing her to be born as a vampire. However, Farmworld Marceline said she is half demon and her father is demon so her mother might have been mortal. Given that there is no evidence that being bitten is what caused Marceline to become a vampire, this possibility is valid. If we assume that vampires age very slowly, she could still be "a child" by the time of the Mushroom War. It could be possible that the memory Finn and Jake viewed of Marceline as a child shows her when she is 400 years old. If she currently appears to be 18 but is 1000, some simple math (18/1000 = x/400; x= 7.2) shows that if we assume a linear change in what age she appears to be over time, when she is 400 she would appear to be about 7.2, which she indeed does. It is possible that being bitten did not turn her into a vampire, but simply granted her vampire powers. This means she could have been bitten at any time before she moved in with Ash, but after her dad ate her fries. This possibility suggests that the mushroom war occurred 600 years ago. But in the episode "Finn the Human" It is stated that the world was frozen for around 400 years. 600+400=1000. This speculates that the Mushroom war era did really last 600 years.
 * Because Marceline's father was a demon and not a vampire, it's possible that her physical characteristics of grayish skin, pointed ears, fangs, immortality, and shape-shifting abilities are actually demonic, not vampiric. She appears to not be as intensely demonic as her father so perhaps her mother was only a human and died long ago (she's seen playing by herself with Hambo in front of a house that looks war-ravaged. Her mother isn't around which is evidence that she was perhaps killed). She has a Christian painting on the wall of her house (confirmed to be the Virgin and Christ-child), which doesn't seem like something a demon would want to own, so perhaps she got it from a human, Christian mother. The first time we see her with bite marks is when she's with Ash. If Ice King is about 1,000 and was only about 30 when the war began, then Marceline's age depends on whether or not demons age slowly (altering her age when she looked like a child during a war), how long her mother had been dead around the time we see her playing with Hambo, and whether or not she and Ice King were witnessing the same war. There isn't evidence that she was aging slowly up until the time she was bitten (the diner ruins in the fry-eating scene look like typical post-apocalypse not magical Ooo scenery) so it's likely she was the age that she appeared to be. If the war that Ice King experienced as a human being is the same one that left Marceline alone in the ruins of her home, then he would only be about 25-30 years older than her. When she was bitten, she could have been permanently frozen in her late teens and remained that way for the next millennium.
 * Marceline's Father, Hunson Abedeer, is a demon, but not just a demon, the Lord of Evil. He rules the nightosphere, a hell-like place. He probably fell in love with a human and they had a child, Marceline. Marceline was part demon, from her father, which gave her a vampiric look, including pointed ears, almost white skin, and fangs as a little girl as seen in her memory as a little girl in "Memory of a Memory." She didn't have the bite marks that turned her into a vampire in that memory, showing that she probably wasn't a vampire when she was little, just part demon. In the same episode, she didn't float like Marceline does as a vampire, she hops from trees in a non-human like way, probably because of her demon side. Marceline grew up around the era of The Great Mushroom War, the war that caused the apocalypse, and her and her father survived because of their magic powers, but her mother most likely died in the war because she was a human. Marceline does have some memory of her though, because in "Henchmen" she says she likes the pain the sunlight gives her because it reminds her of when she was little and got injured and her mom would "patch her up." She says this with fondness, so she must have had an somewhat affectionate relationship with her. We think she is deceased because in the show, she is rarely mentioned and never seen, where as her father is mentioned and seen multiple times on the show. Marceline's memories of her mother seem to only be from when she was little, which fits because in "Memory of a Memory" she is seen as a little girl playing in the burning ruins of a city, probably the aftermath of The Great Mushroom War, and her mother wouldn't have survived so she must have been even younger when her mother was alive. In "Memory of a Memory" it is shown that Marceline is very emotionally attached to a beat up teddy bear named "Hambo." She is seen playing with Hambo as a little girl after the mushroom war, and and she states that Hambo is her only friend, probably because almost nobody survived the mushroom war and it would take a long time for society to re-create. In another memory Marceline is seen to have grown up and appears a teenager and still doesn't have any bite marks, proving further that then she wasn't a vampire because vampires don't age. Since her father is an immortal demon but her mother was a human, she probably aged very slowly. In the memory her father is eating her french fries ( even further proof that she then wasn't a vampire, because Marceline only eats red things so she would probably not desire fries if she was a vampire ) in an abandoned diner. She catches him and gets upset. This along with other things caused Marceline and her fathers relationship to be strained for a long time, and in the future Marceline would write " The Fry Song," a song about that situation and other things to hurt her and her fathers relationship. In her next memory Marceline and her then-wizard boyfriend Ash, are moving in together in a tree fort that would later become Finn and Jake's home. In this memory she does have bite marks, and from this memory on her physical appearance remains the same, so Marceline must have turned into a vampire between when her father ate her fries and when she moved in with Ash. There are no clues that point to how she became a vampire though.
 * One possibility as to how Marceline became a vampire is that she was bitten by the Vampire King and transformed so that he could make Marceline his queen. Going along with the theory that she is half demon and half human, it's possible that aside from the physical appearance inherited from her father and perhaps some supernatural strength, she otherwise would've aged normally (or at least close to normal). This is supported by the similar backgrounds between the scene of her as a small child and the scene of her as a teenager. If this is true, then we can assume that some years after the scene where Marceline finds her dad eating her fries, she was bitten and turned into a vampire. This would've stopped the aging process and place her at her current appearance of late teens to mid twenties. Since vampires (classically) only feed on victims and don't normally turn people into vampires, it is reasonable to assume that whoever turned her into a vampire intended to make her their companion. This is especially true if vampires in the Adventure Time universe don't need to drink blood to survive. Marceline also would've been an unlikely candidate to feed on, given her demonic appearance. This leads me to believe that it was the Vampire King who turned Marceline into a vampire, intending to make her his bride (or possibly to save her from certain death). Pendleton Ward has stated that Marceline killed the Vampire King, so it follows that either immediately or some time after she was transformed by him, she killed him for biting her or for another reason. If we can assume that the memory of Marceline as a teenager (seeing her dad eating the fries) happened over nine hundred years ago, and the scene with Ash happened fairly recently (Marceline is seen with bite marks, Ooo looks the same as it does in the show, etc.) then the gap between these scenes could be many centuries. This implies that aside from Marceline being bitten and turned a few years after the Fries scene, the killing of the Vampire King could have happened at any point in that time span.
 * In "Finn the Human", farmworld Marceline, bare of bite marks on her neck and thus assumably not a vampire, explicetly states that she is 1000 years old and that she is a half demon. Although not directly stating that her mother is human, it can be assumed that she could be. This also implies that her mother is not a demon. Looking much older than her regular self, understandable as she is not a vampire in this altered reality, she is however still alive despite her old age. This may mean that she gained immortality, has a very long life span, or inherited immortality from her father. Due to the inheritence from her mother's side and the fact that she does not have shape shifting abilities that were displayed, she still ages in appearance. This may suggest that her appearance displayed in "Finn the Human" could be her actual physical appearance if she was not bitten.