|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 #46 is the forty-sixth issue of the Adventure Time comics. It features the additional story "Water Strike" by Mady Martin.
When one of Joshua’s old spells wears off, Finn and Jake find themselves facing an old childhood friend that neither of them can remember!
Finn and Jake are swimming to a temple beneath a lake with one of Joshua's alarmed messages in tow. Joshua tells them that he needs them to follow his instructions to take care of something there. He tells them that inside the temple is an important statue, which the boys find immediately. Joshua continues to give instructions for how to get to the statue so they can protect it from an intruder. This exasperates the two since all of it is now irrelevant.
Waiting for the message to move on, Finn suggests they move the statue from under the crumbly ceilings. Jake jokes that some mushrooms are the intruder and kicks them, not realizing that something is behind him. Just as they are about to move the statue, a mushroom beast attacks Jake. He tries to fight it off, but gets infected by the spores. Finn tries to help, but Jake says he needs to get the statue to a safe place, then the beast punches him. (Ironically, Joshua mentions a patch of mushrooms he needed to clear out at this point.) Finn decides to help Jake over saving the statue, letting it fall and break. He defeats the mushroom beast, but the temple collapses and floods with water. Fortunately, the duo makes it to the surface unharmed, and the sunlight cures Jake's mushroom infection.
As they reach home (after getting mushroom pizzas), Jake feels bad that they failed Joshua's mission. Finn assures him that Joshua would've preferred he was saved instead of a statue. They enter the house, only to find an unknown girl lounging on the couch. She asks them if they found out what set off Joshua's alarm. Finn awkwardly asks if they can help her, and she says they can help by giving her pizza. Jake says they don't give pizza to intruders, and Finn demands the girl to tell them who she is and why she's in their house. The girl realizes that they don't recognize her. Jake asks BMO if they let her in, and BMO says that the girl, whose name is Gata, isn't a stranger. Gata thinks that Finn and Jake may have been cursed to not remember her, and BMO tells them that Gata is like their sister. As Finn struggles to comprehend this, the house is shown to have changes (a third bed, name in video game high scores, and clock hand) implying that Gata has always been there.
At the remains of the underwater temple, Joshua's message says that the statue must stay unharmed and that the things in the temple are meant to be forgotten. The holo-message player is shown to be next to the broken statue, which resembles Gata's face.
Marceline is at home about to take a shower. After applying shampoo, she turns on the faucet, but no water comes out. She checks the other faucets around the house and even a well, but there is no water to be found. A pair of birds tell her there's no water in the sea or sky, and Lady Rainicorn is fading from no water in the air. Marceline calls this an emergency and sets off to find out what happened. Finn and Jake are at a dried-up river, wondering where the water went. They see Marceline and Lady coming and ask what they're doing. Marceline tells them that they came to see the source to find out about the water's disappearance. Many other people, including Princess Bubblegum, also come for the same reason. Finn calls an investigation, and everyone follows the river bed for a few hours. Jake gets thirsty and resorts to licking his sweat. Finn thinks it's gross, but also clever. Marceline then hears something, and Jake identifies it as crying. They all see that it's a sad little water drop. Everyone rushes to get her, but Marceline stops them. She says the water drop isn't enough for all of them, but might know where the rest is. She kindly asks the water drop what's wrong, and the water drop says that her mother and sisters left her behind since she couldn't keep up. Marceline says they can take her back to her mother, so the water drop shows them the way. After a while, they find the water drop's mother, Water Princess, on strike alongside the other water drops. Everyone asks what's going on, and Water Princess angrily states that she is mistreated by them all, despite everything she does for them. For example, Marceline leaves the tap running, Bubblegum pollutes the rivers with her factory, and Finn throws garbage into the ocean. Everyone feels guilty after hearing this. They apologize and agree to make things right, which makes Water Princess shed tears of joy. She ends her strike and starts playing water games with them.