Finn is hanging out with Marceline when she asks him to beatbox to her new song, and starts by asking him not to laugh because it's going to be personal. Then she sings about her dad and how he left her. This tears Finn up, and he summons her dad... from a hell dimension called The Nightosphere. Because it turns out that Marceline's dad is an evil demon who doesn't approve of her way of life and likes sucking out peoples' souls, which is why she sang songs about him instead of inviting him over. He takes Marceline's bass (which is actually their family axe) and walks out when she starts yelling at him.By the time that a pissed Marceline and Finn have caught up with him, Dad has already sucked up the souls of a lot of denizens of Ooo. And grown really big. Finn tries to attack him, while he is distracted by Marceline's swearing. Finn discovers that the sucked up souls are literally in him... in his neck... whatever it is, and tries to free them, but instead drops himself and Marceline's bass to the ground. Marceline is satisfied and turns around to go back home, while Dad turns back to sucking the souls. Finn, exasperated, turns on the recording of Marceline's song he still has on him. It forces Marceline and her Dad to finally talk about it, and Dad starts apologizing... at which point Finn climbs up him and cuts him with his sword, freeing the souls, and immediately sends him back to The Nightosphere the same way he was summoned. Marceline is mad at Finn for first embarrassing her and then interrupting her reunion with her dad... but ultimately, not very much, because being near him is exhausting.
- Absentee Actor: Jake appears at the last second, but he doesn't have any lines.
- Attack of the 50-Foot Whatever: Marceline's Dad by the moment Finn and Marceline catch up with him. If only Jake were there...
- Blatant Lies: This line:Fluffy Person: Huh? Who the fluff are you?
Marceline's dad: Well, I'm sure not the guy who's gonna suck out your soul...
- Bring My Brown Pants: The Ice King soils himself (according to dialogue) on seeing Marceline's Dad's Nightmare Face.
- Call-Forward: Much later in season six, the comment about Gunter being the most evil thing Marceline's Dad had ever encountered turned out to be true.
- Card-Carrying Villain: Marceline's Dad describes himself as "completely evil".
- Catch a Falling Star: Subverted. Marceline sees that Finn and her axe bass are falling from a great height. She rushes over and catches... her bass just in time, and lets Finn hit the ground.
- Comically Missing the Point: This exchange:
- Complete Immortality: According to Marceline, her father can't be killed.
- Did You Just Flip Off Cthulhu?: When Marceline's Dad attempts to claim Gunter's soul, Gunter bitch-slaps him.
- Eldritch Abomination: Marceline's Dad. Since he's Oo's equivalent of Satan, it's not surprising.
- Even Evil Has Loved Ones: Marceline's Dad may be a soul-sucking Eldritch Abomination who is heavily implied to be Satan, but he still loves his daughter.
- Eviler Than Thou: Gunter to Marceline's Dad. See Killer Rabbit.
- Faux Affably Evil: Marceline's Dad acts fun, but is also a soul-eating demon. At one point, he teaches a fluffy person to be grateful to be alive, so that it will be more horrifying when his soul gets sucked out.
- Freudian Excuse: Marceline has some hard time with her father, which is expanded on later on.
- Hypocritical Heartwarming: Parodied.Ice King: No one sucks the life from my penguins except me! And maybe polar bears, because that's just nature, Gunter.
- Killer Rabbit: Gunter No Sells Marceline's Dad's attempt to suck his soul, and slaps him. Marceline's Dad then says that Gunter is the most evil entity he has encountered so far in Ooo.
- Nightmare Face/Take Our Word for It: Marceline's Dad's distorted face that terrifies the Ice King, which is too scary for us to see.
- Noodle Incident: "Daddy, why did you eat my fries?"
- Shout-Out: Marceline's red striped sweater is similar to that iconically worn by Freddy Krueger.
- Skewed Priorities: Marceline is more concerned by the fact that her dad ate her fries than by the fact that he's a soul-eating Eldritch Abomination.
- Take That!: When Marceline's Dad attacks the Marauders, the leader has just boasted about killing someone who annoyed him by talking about the idea that the Earth is expanding, a crank theory which, among geeks, is notoriously supported by comic artist Neal Adams.
- Your Mom:
- Your Soul Is Mine: When summoned into the Land of Ooo, Marceline's Dad proceeds to suck the souls out of everyone he meets. Well, almost everyone. He initially tries it on Finn, only to be stopped by Marceline.Marceline: Dad! You can't suck out my friends souls!Hunson: *laughing* Oh Marceline. I never know what's gonna set you off!