"The Lonely Planet" is an episode of Wander Over Yonder.
Wander and Sylvia encounter a lonely talking planet named Janet, whose landscape changes based on how much Wander does for her. But whenever Wander wants Sylvia to join in, Janet repeatedly separates Sylvia from Wander, and vows to have him all to herself.
At the beginning, Wander is on a dark, deserted planet trying to come up with something to describe it. He ends up describing it as cute, which he soon hears a voice, turns out it's coming from the planet. Wander introduces himself to the talking planet and asks for her name, but the planet never had a name before and believes she always liked the name "Janet". Wander decides to call her that and she is happy to see him, but is sad because she never had any visitors. Sylvia later approaches and Wander introduces her to Janet, but she doesn't seem pleased to meet her and freezes her, to which Sylvia takes Wander and starts to leave.
Janet begs Wander not to go and suddenly an ocean appears. Wander swims happily in the water and invites Sylvia to join her, but every time she tries to do so, the water rolls away causing Sylvia to get hurt by a rock. Janet then sprouts a pair of mountains for Wander to spin dry on, but when Sylvia tries it, the mountain springs stalagmites, harming her. Wander obviously doesn't notice any of this.
Wander is happy the day can't get any better, and Janet grows a tree and changes the sky to a sunset for Wander to watch. He invites Sylvia up, but Janet only sprouts a small bush, leaving her to climb up the tree herself. Janet then gives Wander four other different sunsets, but ends them early just as Sylvia arrives. At the bottom of the tree, Wander sees the bush Sylvia was hoisted on as Poison Jivey, and Sylvia's tail swells up as a result.
Later that night, Wander and Sylvia are sitting by the fire, Janet thanking the former for everything he's done for her. She suggests Wander should stay, but Sylvia points out they're only staying tonight, which doesn't please Janet so much. While Wander and Sylvia are sleeping, she sprouts a mountain to separate them, then faces Sylvia next morning and sends her down a river.
Wander awakens to find that Sylvia's not here, but Janet stops him, lying that Sylvia took a hike, and gives him some pancakes for breakfast. While he's eating, Wander begins mentioning things he likes about Sylvia, leaving Janet to end the breakfast early and give him pie for dessert. After eating, he starts to walk his "breakfast belly" off and wondering if he won't find Sylvia on a hike. Janet stops him and presents him with a cottage, and hopes he likes it. Wander starts to get scared, but he soon hears Sylvia's voice and tries to call out to her, but Janet says she'll take care of her, so she harms Sylvia and eats her up.
Inside the cottage, an exaggerated Wander complements on Janet and states he and Sylvia should leave, but an angry Janet lies to him and says Sylvia left, and now they are together until the end of time. Wander begins resisting a kiss from a plant Janet makes, just as Sylvia emerges from the floor and attacks it. She and Wander begin leaving, but Janet changes her landscape to a field of volcanoes, trapping them in her orbit and firing a lava ball at them. As the two admit each other's friendship and approach their inevitable demise, the lava ball suddenly stops and becomes a steady meteroite. Janet begins crying and Sylvia insists they'd leave, but Wander refuses and wants to go back.
The two return to Janet and she apologizes for what she did earlier, and reveals she always wanted a friendship just like Wander and Sylvia's. All of a sudden, the meteorite from earlier appears, now a moon named Maurice, and begins flirting with her. Maurice says he finds himself attracted to Janet, which starts a relationship between the two. Wander suggests they say goodbye, but Sylvia instead says they should let them have their space as they leave and Janet and Maurice continue talking to each other.
- Before the episode tittle appears, Janet's flower has two leaves on the left side. But after Wander says "Well, that is some sort of shame!" then the left side has just one leaf, and the right side has two leaves.
- When Sylvia flies down from the hill, Janet makes a rock fly up to hit her, leaving a big mark in the grass. But in next scene, when Sylvia falls to the ground, the mark disappears.
- In the house Janet makes for Wander, many pictures of Wander cover the walls. However, the pictures differ significantly between the first scene and the second scene.
- The title refers to Janet, who is lonely and wants Wander to be with her.
- Lord Hater and Peepers don't appear in this episode.
- This is the first time someone forces Wander and Sylvia to be apart.
- This is the first time a character has a crush on Wander.