Finn and Jake follow the Lich to the Citadel, where Finn meets his long-lost father.
Tropes:
- Abusive Parents: Martin falls into the neglectful category; he can't even be bothered to remember his son's name, calling him "Flynn" at one point. He also manipulates Finn's desire for connection to get what he wants, abandoning Finn as soon as the going gets tough.
- The Alcatraz: The titular Citadel. Inverted for the Lich, who turns it into a Cardboard Prison in a matter of minutes. To the Citadel's credit, it wasn't even designed to hold the Lich in the first place.
- Ambiguous Situation: Martin doesn't seem to remember Finn at all and gives vague, barely substantial answers when Finn asks about abandoning him. Is he really Finn's father? Or just a random criminal who took advantage of the weird kid claiming to be his son to escape the prison and then got away from him as fast as he could?
- An Arm and a Leg: Finn gets his right arm torn off while trying to pull back the platform his dad is trying to escape on.
- Babies Make Everything Better: Tree Trunks is about to ask Mr. Pig for a divorce (Or possibly a dog) before Jake brings them the baby Lich to raise.Tree Trunks: Oh! This changes everything!
- Bittersweet Ending: The Lich is defeated and is reverted into a baby but in the process, Finn learns the Awful Truth about the true nature of his father and also ended up losing his arm after Finn tries to chase his own father.
- Bloodless Carnage:
- Getting a limb ripped off would've been messy, but the grass blade takes over Finn's entire arm and is reduced to a smooth nub when it gets removed.
- Martin's shin is stripped to the bone by a stray laser beam of white hot death. Not a single drop is spilled.
- Buffy Speak: The guardian blood is full of "good nooch" which apparently translates to healing goo that keeps the prisoners alive and in stasis.
- Daddy Had a Good Reason for Abandoning You: Finn and Jake speculate that his dad had a reason for abandoning him, but he does not.
- Doorstop Baby: Tree Trunks and Mr. Pig are ecstatic to find the baby Lich at their door.
- Fantastic Medicinal Bodily Product: The Guardians' blood can heal wounds and regrow flesh and muscles — but not missing limbs. This can extend to an entire skeleton, as the Lich is unfortunate enough to experience.
- Foreshadowing: Martin describing the skin of his healed leg as "smooth like new" foreshadows how Finn uses the Guardian blood to "reboot" the Lich.
- Groin Attack: One of the monsters in the Citadel, which consists only of a lower torso and legs, gets hit in the crotch with a skull.
- He Will Not Cry, so I Cry for Him: Finn is too shocked by everything that happened up to and including losing his arm to do or say anything after it happens. When Shelby emerges from Jake's ear, he's seen crying.
- Jerkass: Finn's father, Martin, is a huge one. He abandoned Finn for seemingly no reason, does not care about him in the slightest, and his actions leads to Finn losing his arm. Oh, and he's a peer to cosmic criminals.
- Just Between You and Me: The Lich reveals his entire plan to raise an army of world-destroying monsters and wipe out all other life in the universe to Finn. He apparently felt safe in gloating because Finn was in no apparent position to stop him at the time, and only managed to thanks to the Guardian blood.
- Nice Job Breaking It, Hero: Finn and Jake freeing Martin results in a charismatic criminal giving a bunch of stronger, world-destroying criminals a leader who helps them escape.
- Nice Job Fixing It, Villain:
- The Lich actually falls into this twice: First, by waking Prismo himself instead of letting Finn and Jake do it, he allows them to get to the Citadel without being imprisoned. Second, by going to the Citadel he came within proximity of a substance capable of truly defeating him: Guardian blood.
- Also, one of the cosmic villains fighting the Guardians accidentally opens a portal to Ooo, which allows Finn and Jake to easily get home, taking the resurrected infant Lich with them.
- One-Winged Angel:
- The Lich sheds Billy's skin and becomes a giant horned skeleton.
- In order to keep Finn's dad from escaping, the grass blade completely takes over Finn's arm and gives him Super-Strength. Unfortunately, it was not enough and Finn gets his arm torn off.
- Overly Long Gag: When a guardian blasts a laser, cutting through Martin's right leg revealing a bone, Finn says "Uh-oh" 15 times.
- Raise Him Right This Time: The Lich's fate after being reduced to an innocent infant.
- Revive Kills Zombie: Played with when the Lich is defeated for good by the healing blood touching him, but is instead turned into an innocent, flesh and blood infant instead of dying.
- Shut Up, Kirk!: The Lich to Finn. One word: "FALL."
- Stripped to the Bone: A beam from one of the Guardians hits Martin in the leg, burning all the flesh off his right shin and calf. He takes it surprisingly well.
- Story Arc: Both continues the Lich's and starts a new one with Martin.
- Thinking Up Portals: One of the cosmic criminals is referred to by Martin as "a voidcaster" (though it's unknown whether this is a job or a species), who is capable of opening portals by waving some sort of wand. One of these ends up being how Finn and Jake go home to the Candy Kingdom.
- Villainous Breakdown: The Lich finally loses his cool after being exposed to the Guardian blood, which begins 'rebooting' him into an innocent infant. He spends the entire time screaming in a complete panic and trying desperately to get the regrowing flesh off him.
- Wham Episode: The Lich is destroyed and reborn into a baby who's left with Tree Trunks and Mr. Pig, Finn meets his dad who turns out to be an annoying jerk who abandons him and runs on with a group of cosmic criminals, and Finn's long foreshadowed loss of his arm finally happens.
