Finn and Jake follow a Sea Lard, and in doing so, are led to a strange new world.
The episode begins with Finn awakening on his bed. He appears to be uncomfortable, and then discovers their Sea Lard that was the cause for this discomfort, which Jake then mentions to have been the eighth time. Jake is disgusted by the Sea Lard, and suggests they dispose of him. So, Finn and Jake go outside and dump the Sea Lard in the pond outside their Tree Fort. They then ponder whether the lard will be okay. Shelby comes out from Finn's armpit and informs them that sea lards are salt water fish, and that the pond outside is fresh water. After hearing this, Finn nonchalantly takes off his pajamas, revealing his red-and-white underpants, and dives in to rescue the sea lard.
Jake joins Finn as he continues to swim after the sea lard, eventually they reach a narrow tunnel at the bottom that leads them to a grotto. They resurface and the Water Nymphs are singing a song. One of the nymphs welcomes Finn and Jake, asking if they would like hot dogs. They decline the offer, as they are searching for the sea lard, adding that he is a salt water fish. The nymphs then correct them that Sea Lard's are mammals, which Finn pretends he knew while silently showing rage at Shelby. The duo spot the lard, and see him moving towards a whirlpool/vortex. They chase after the lard, despite the nymphs warning not to go near it. As Finn and Jake dive through he whirlpool/vortex, a nymph warns them not to touch the purple stuff.
Finn and Jake arrive in a different dimension, the animation changes, and colors are altered. Jake spots the lard and the two chase after it, only for Finn to get distracted by singing "Lards," and Jake paying attention to a butterfly resembling Lady Rainicorn. The two venture off acknowledging the environment around them. They discover the Sea Lard's new position, however again get distracted, this time by a leaf version of Marceline. She sings Rather Be Anything, and then reminds them of their reason for being there after she finishes her song.
Finn and Jake question the lard's reason for evading them, as they are trying to help him. The purple stuff that the nymphs had warned them about ends up touching Finn and Jake, and appears to affect their memories. Princess Purple Patch introduces herself, but leaves in shame for "purpling" the two. Finn and Jake begin to lose nearly every memory of who they are, so they re-identify as Boy and Dog.
The two hear a creature weeping, later revealed to be Bushboots the Little Apricot Ant-Eater, whom is mourning over her loss of her rolling pin, which Finn and Jake then set out to search for. After looking around, Bushboots's "rolling pin" has actually turned out to be the Sea Lard, however the duo have no recollection of him, nor the fact they were previously looking for him. Bushboots uses him to roll her dough, unfortunately it possesses remarkable speed, and escapes. Although he does not wish to be a rolling pin, that Finn and Jake had just deduced, they still attempt to return him to Bushboots.
The two then encounter a bee called Bee-Mo, who sounds like BMO, that recites a poem to them and tells them what to do. They continue on to the pond, which was the place they arrived to the alternate dimension. The pond is revealed to be sentient, and invites them to jump in. Due to forgetting the events prior to being touched by the purple stuff, they do not know that the pond is their passage to their world. The Sea Lard uses this opportunity of the heroes' uncertainty to shove them in the vortex the pond created, afterwards jumping inside.
The scene shifts back to Finn and Jake's world, where Jake is telling BMO of their journey beyond the grotto, describing the characters they met and comparing them to the characters in their world, and Ice King overhears and jumps in the treehouse. Jake tells BMO that the real hero was the Sea Lard, and that there was a purple lady with many resemblances to the Ice King. Ice King is then denied knowledge of how to get there, and asked to beat it. The episode finishes with Finn tucking in the Sea Lard in bed, and apologizing for the treatment they had given him, and wishing him a good night's rest.
- Water Nymphs
- Butterfly Lady Rainicorn (Lady Rainicorn)
- Princess Purple Patch (Ice King)
- Bee-mo (BMO)
- Singing Flower (Marceline)
- Bush Boots (Tree Trunks)
- Pink Pond (Princess Bubblegum)
- Weirdo Finn
- Weirdo Jake
- Mr. Pig (Grotto Version)
- Choose Goose (Grotto Version)
- Mr. Fox (Grotto Version)
- This is the third canon episode to being animated by a guest star, the other two being "James Baxter the Horse" and "Guardians of Sunshine."
- One of the title card concepts (shown below) is based on the final shot of the 1997 anime film, The End of Evangelion.
- Finn won the Sea Lard in a raffle in "Princess Potluck."
- Jake encounters a small pink thing, and tells it, "You are so crazy…," the same dialogue he had told Lady Rainicorn in "Slumber Party Panic." This thing slightly resembles Lady Rainicorn as well, and the animation it is given is very similar to Lady's appearance in "Dad's Dungeon."
- This episode was previously titled "Beyond the Grotto of the Water Nymphs."
- This episode features 7 minutes of guest animation done by Alex Butera and Lindsay Small.
- When Finn and Jake enter the Water Nymphs' world, Finn is in his underwear. But in the shot where Finn meets the Water Nymphs, he has his shirt back on, only to lose it again in the next shots.