|The following information is from the Adventure Time comic book series. It may not be part of the same canon or continuity as the animated series.|
Issue #51 is the fifty-first issue of the Adventure Time comics.
After too many back-to-back quests, Jake and Finn disagree on how important doing this hero stuff really is.
Hot Dog Princess and her Hot Dog Knights stand at a cliff by the seas. The knights note that Finn and Jake have been underwater for three days and think they drowned. Fortunately, the adventurers emerge from the water, donning crustaceous armor and riding dolphins. Finn presents Hot Dog Princess with the hot dog's treasure: a tennis ball that got thrown too far. Grateful, Hot Dog Princess invites the two to their celebratory party, but Jake just wants to go home because he's tired and hungry. Finn says he shouldn't be rude and that there might be food at the party. Later that evening, the food at the party turns out to be various mustards, to Jake's displeasure. Not too far from the Hot Dog Kingdom, a ghost appears from an opening in the ground. He touches a yak and turns it old. Finn is chatting with the hot dogs, but Jake tells him that he wants to go home. Finn says that being gracious with their gratitude is important, but Jake writes off that they made their appearance and tells everyone goodbye. Finn tries to cover his rudeness, and Jake stretches both of them away. The ghost then appears behind the hot dogs.
The next morning, Jake decides to make forever sauce now that he isn't adventuring. Day becomes night, and Jake is about to serve pasta for dinner, but he is interrupted by a knock at the door. Annoyed, Jake answers the door and finds the now-elderly Hot Dog Knights, who try to ask for help. Jake sternly says no and slams the door, but Finn tells him to let them in. Hot Dog Princess (also old) explains that a ghost did this to them and beseeches the heroes to remove the curse. Finn says they'll slay the ghost and restore their youth, but Jake is less than enthusiastic. Out in a field, Jake wants to talk about all the questing they do, but Finn then finds the ghost. Finn goes in to attack with Finn sword, but stops when the ghost reveals that he knows of him. The ghost says that everyone in Ghost-A-Rica knows of him, as he killed a lot of them when he was little (not this ghost, who was killed by a falling rock).
The ghost says that he came to the overworld to get Finn and Jake's help for a problem in Ghost-A-Rica. Finn isn't completely sure, and Jake grumpily shouts about his pasta. Finn tells him to chill and asks the ghost why he's making people old. The ghost says he is cursed to do it, but doesn't mean to. He explains that the Governor of Ghost-A-Rica made magical artifacts (shackles around the neck) that turn ghosts into life sucking agents. They touch living beings to drain their youth, then put the youth into a large pot to make an elixir. When it gets strong enough, the Governor will drink it and come back to life. He'll likely just enjoy some more years of life, but many people will be made old. Finn says they have to stop this Governor, but Jake refuses because he wants a break from adventures. Understanding, Finn allows Jake to skip the adventure and is ready to go on his own. The ghost thanks him for offering his aid, but mistakenly touches his face in excitement, turning him old.
Jake asks Finn if he's okay, but Finn starts to act like a typical senior. Jake tells the ghost to make him young again, but the ghost says the only way to do that is for him to drink from the elixir. Jake realizes they need to get the elixir, then realizes he has to go on another quest. Finn assures that he'll still help, despite his sudden aging. The ghost leads them to the opening he came from. He tells them that he has to get back before he gets in trouble and that Finn is slowing them down. He also tells them to go through the caves until they meet the underworld's guardian, who makes sure that the dead don't leave and the living don't enter. Jake asks how they can get past, but the ghost says they'll figure it out like he did and goes ahead. Jake carries Finn through the caves so he doesn't get hurt. As they travel, Finn apologizes for not noticing Jake's frustration. Jake say it's okay. He explains that they were adventuring since Finn was little, but that he liked to do other things since he grew up faster. He let Finn grow at his own pace and did the things he liked doing, which was saving princesses and stuff. He thought Finn would grow out of it after maturing. He finishes by saying that he still likes adventuring, but it feels more like responsibility than fun and he just wants a break. Finn imagines that his younger self would respond differently, and thinks that they're lucky to be in a time where one person can make a difference for others. They reach the guardian at the portal to the underworld, but he tells them to go home.
Finn asks why, and the guardian says only the dead may pass. Finn figures that "dead" means "without vital life force." He says the Finn sword is made of his essence, so he could go through if he leaves it with the guardian. The guardian guesses that makes sense and allows it, but doesn't see why Finn would want to leave the living world. Finn says he has his reasons and winks. As he starts going through the portal, Jake asks what he should do. Finn winks again and gives a thumbs-up. The guardian says Jake has to go back, but Jake offers his stretchy powers as a weapon of vital life force. Finn winks some more and gives two thumbs-up. When Jake realizes what he's doing, the guardian takes his powers. After confirming he can take them back if he returns, Jake joins Finn on the other side. Finn is glad they got into the underworld without dying, but Jake reminds him that they have no means of defending themselves. Seeing that is true, Finn wishes luck to Jake, dashes through the portal, and throws Finn sword to him. Bothered, the guardian locks down the gate. Jake, now stuck in the underworld, picks up the Finn sword and nervously tells himself it's adventure time.