"Beyond this Earthly Realm" is the eleventh episode in the fourth season of Adventure Time. It is the eighty-ninth episode overall.
The episode opens with Finn and Jake descending down a dark mineshaft-like tunnel lined with boulders, with the help of Jake's stretchy powers - he has wrapped one arm around a rock outside the cave entrance and is lowering himself down along with Finn. They both wear lights of some sort on their heads: Jake, a candle stuck on top of a colander he wears as a hat, and Finn a flashlight taped to a helmet. Jake is tired and wants to go home, but Finn still wants to search for a "mystery cave." They fall on top of each other when they reach the bottom of the shaft, but Finn quickly notices a small opening. They both crawl out into a much larger chamber containing a porcelain lamb with a red crystal embedded in its forehead, resting on a stone altar surrounded on three sides by stairs. Finn walks up to the lamb and reaches to touch it, looking fascinated, but from behind Jake stops him and says it might have a sacred significance. Finn ignores him, saying he wants it for his "sacred bathroom." When he reaches forward and touches the lamb, a bright reddish-pink light bursts from the lamb's crystal, and when the light shrinks and retracts back into the lamb, Finn is nowhere to be seen. Jake runs up to the lamb and finds that the lamb now has Finn's sleeping face, and the red gem has disappeared. Jake exclaims, "Finn's become one with the lamb!" Meanwhile, Finn picks himself up off the ground in the same room not far from the altar, but the cavern has taken on a red glow, and he is suddenly surrounded by many strange semi-transparent creatures. He yells to Jake when he sees him at the altar, but his friend cannot hear or see him and does not turn around. Jake sadly wraps up the porcelain lamb carefully in a cloth, vowing that they will "get through this" and seeming to think Finn is inside the lamb. He sits on the floor, holding the lamb, and yanks his tail twice before it starts growing shorter, dragging him back toward the mineshaft. Finn follows him home unseen and unheard.
In their tree fort Finn and Jake sit on the couch across from BMO, but Finn is invisible to the other two along with the strange creatures everywhere. Jake is pondering how to "free" Finn. BMO begins to make electronic farting noises, saying Finn always liked it when BMO did that. Finn laughs, though the others cannot see this. This gives Jake the idea of doing all Finn's favorite activities to get him out of the lamb. He tells BMO to play Finn's "favorite song," which turns out to be a childish song he liked when he was two years old. The creatures surrounding Finn laugh when they hear the song, and Finn walks out of the house through the wall when he finds he cannot touch BMO to stop the song embarrassing him.
Sitting on the branch of the tree fort hopelessly, Finn watches Ice King chase what the old wizard thinks is "leaf princess." Ice King grabs the leaf and falls on the grass, and Finn says, "It's just a dumb old leaf, you dumb old Ice King." Finn is surprised when Ice King responds, "I know, but it's mine," and he asks how he can see him when nobody else can. Ice King tells him he is trapped in the "spirit realm," and he can see him because of his Wizard Eyes. The Ice King offers to help Finn because he is his friend, and they go to the Ice Kingdom together. Ice King shows Finn all the weird creatures that go about his home, and when Finn asks where they come from, the Ice King replies "all over the universe." Ice King says he cannot touch them or kill them, and that he hates them. He tells Finn that putting all the creatures into the spirit hole in his basement is the only way to get out of the spirit world. Finn obliges and begins throwing and kicking creatures into the hole, which sounds like it is filled with liquid.
Back in the tree fort, Jake is trying to coax Finn out of the lamb by playing Kompy's Kastle (a video game of BMO's) with it. Despite his hopeful, positive attitude, Jake is still unsuccessful.
In Ice King's basement, Finn is plugging up the spirit hole because he has put all the creatures he can find into it. However, Ice King says he hasn't gotten all of them, and shows him an eyeball creature in his bathroom that he finds particularly creepy because it always stares at him. Finn catches it and puts it in the hole, but Ice King says there's one last creature, and it is "pretty much the worst" because it always leaves its gross heads lying around. He calls this last creature "the Dead One." Suddenly Ice King is chased around by one of the heads and screams hysterically at Finn to get rid of the last creature. Finn finds the creature and chases it with more difficulty than the other creatures gave him, and nearly falls into the spirit hole when he manages to get it in. He finds that, interestingly, the spirit hole leads downward into the cavern where he found the lamb earlier on. When he climbs out and plugs up the hole for the last time, he searches for the Ice King and finds him joyfully bouncing on his bed and singing that Finn will be trapped in the Spirit World forever, his one and only friend. Finn threatens to reopen the spirit hole when Ice King reveals that he tricked him, but Ice King hurriedly changes his plans and promises to help him break the porcelain lamb, setting him free.
Ice King returns to the treehouse wearing a layer of ice as armor, and Jake, who was still playing games, gets up and defends the lamb from the Ice King, who says he has to smash it because Finn is inside it. Jake quickly shatters Ice King's armor in two punches and pulls off his robe, embarrassing the wizard and causing him to trip onto the lamb. Ice King's face now appears on the back of the lamb's head. Trapped in the Spirit World with Finn and able to be actually touched by the gross creatures, Ice King has a fit, takes Finn's hat and wears it like a shirt, and ends up wailing on the floor again, waving his arm back and forth. Finn notices that Ice King's hand movements are affecting the static on the television screen it passes by, and realizes they can have subtle effects on the material plane. Finn and Ice King work together, levitating leaves and scraps from the floor and swirling them around in air currents, to shift the lamb off the stool it rests on, shattering it on the floor. Finn and Ice King immediately pop back into the material plane as the lamb breaks, and the leaves fall to the floor as Jake wraps Finn in a hug. Jake says "that was beautiful," then sweeps up the pieces of the lamb, saying they should flush it in "the sacred bathroom." They both laugh, but Ice King grabs them and gives them both an unwanted hug, cackling hysterically.
- Ice King breaks the fourth wall in this episode when he and Finn are both in the spirit realm by basically stating how the viewer watches the characters' actions through TV. He describes it as a "clever one-way mirror."
- There is a Cartoon Network Bumper that shows Cartoon Network characters like Daffy Duck, Prince Gumball, Finn, Mordecai, Rigby, and Bugs Bunny counting down from ten, after which Lumpy Space Princess says "drama bomb!" and Jake blows a raspberry. Before the episode aired, one of these bumpers featured BMO blowing a raspberry, which was a part of this episode. The bumper featuring BMO was also a countdown of 5 instead of 10.
- Immediately after Finn is transported to the Spirit World, the portal to Ice King's basement can be seen in the upper part of the cave.
- The skull on a table next to the TV looks like the one that appears at the beginning of the opening theme, except it does not have spikes coming out of the top.
- Finn's neck is quite a bit thicker in this episode than it is in previous appearances.
- At one point Jake and the porcelain lamb are playing a game called Kompy's Kastle on BMO. One of the sounds made is Metal Man's Metal Blade from Mega Man 2.
- Jake's yawn when going down the hole at the beginning of the episode sounds a lot like Chewbacca's infamous roar from the Star Wars saga.
- At least two allusions are made to videogames by Jenova Chen: initially, the Journey 'dragons' seen jumping through the mist in the Ice King's basement, and later the Flower-esque leaf-swirls made by Finn and the Ice King.
- When Finn touches the lamb and is transported to the spirit world, Jake says "Oh, my Jah!" This is a reference to the Rastafari movement because "Jah" is the Rastafari word for God.
- Ice King singing seems similar to the story of Rumpelstiltskin, because a knight discovers the troll's plan when he hears him singing his "song of joy."
- The song "Three Baby Spiders" bears a resemblance to the nursery rhyme "Itsy Bitsy Spider."
- The bandana that was used in "Princess Monster Wife" appears again, but only on Jake.
- When Finn is looking for Ice King, he said, "Where'd you go, Simon?" Simon was the Ice King's original name while he was human, before the Mushroom War, which was revealed in "Holly Jolly Secrets Part II."
- Finn's hair has grown past his shoulders, from when he last took his hat off in "Another Way."
- The spirit creatures and Ice King's "wizard eyes" were both first mentioned and seen in "Mortal Recoil."
- Finn's real ear, from "To Cut a Woman's Hair," was seen after Ice King removed Finn's hat.
- When Ice King says that the heads of the Dead One creep him out despite him being unable to touch them, he flails his hands and is able to knock the head off. However, this could be interpreted as simply flailing about enough to shake the creature off as it was clinging to his body - in this interpretation, he would not have needed to touch the creature.
- When Finn gets trapped in the lamb, he is seen to be sleeping. However, when Jake looks at the lamb shortly afterwards, Finn's face appears to be smiling. This happens twice: first, when Finn gets trapped, and second when Jake is holding the lamb at the tree fort. Also, when he seems to be sleeping his eyes are closed, but when Jake is talking to BMO in the living room, Finn's eyes are open.
- Before Jake enters the Mystery Cave he is seen to be wearing a blue bandana, but after entering the bandana is gone. However, it is possible he could have taken it off before entering the cave.
- When Jake and Finn were playing Kompy's Kastle, the two meters were yellow-orange (top) and red-orange (below), but when the screen turned back to the two meters, the top meter was light green.
- The pickaxe and lantern by the cavern entrance disappear temporarily in the zoom-out, when Finn enters the Spirit World.
- When Jake is seen in the room playing BMO for the second time, BMO's back does not have its features.
- When Jake is shown in the room playing BMO for the first time, there was no table with a skull, a candle, a book, a quill pen, and ink on it in front of Jake; later it is shown that the table was next to the TV and a pencil and what looks like a red pen disappear.
- While Ice King is singing his song of joy, his drum set clearly has the words "#1 BASS" instead of the usual "#1 BABE."
- On the day the episode premiered, during the long preview, there was a quick cut to the Annoying Orange watching the preview on a television and asking Finn if his hat is a marshmallow hat. This was done to tie in with the Annoying Orange TV Series that officially premiered the same night. Regular Show also experienced the same treatment. MAD did not have this special commercial, however, because it premiered the new episode after Annoying Orange broadcast.
- The "strange creatures" that Ice King sees with his Wizard Eyes are explained in this episode as beings of the Spirit World; this appears to explain his bizarre vision when showing his "typical Wizard Eyes" in "Mortal Recoil," but it was unknown at that time.
This episode was censored in some countries. See Censorship of Adventure Time for more information.