Finn and Jake
Finn and Jake are playing with swords when Tree Trunks the elephant invites them into her house to have some of her baked apple pie. The first pie is touched by a fly, so Tree Trunks throws it away, saying that since the flies wanted it, they can have it, and makes another pie for Finn and Jake. As the two of them eat the pie, Tree Trunks asks them what they would do if they could do anything. Finn says that he would catch a shooting star into space to fight space monsters, and Jake would carve his face onto the moon. Tree Trunks says she wants to pick an apple, but it is known as the rare Crystal Gem Apple. It is located in the Evil Forest, and Finn and Jake decide to make her wish come true.
When they reach the Evil Forest, they encounter the Wall of Flesh and try to fight it, but because Tree Trunks is naive, she begins putting stickers on it. The Wall of Flesh flees when Finn cuts off one of its arms, and soon Tree Trunks walks away, following a Skeleton Butterfly. She is attacked by Sign Zombies and begins having a tea party with them, not knowing they want to kill her. Finn and Jake fight off the Sign Zombies and continue their adventure, until they encounter a Brain Beast. Finn goes to fight it, but Tree Trunks' "adventurer's instincts" tell her to put on makeup and seduce the Brain Beast with her womanly charms. Jake has to leap in to save Tree Trunks while Finn attacks the monster's magic gem weak spot. After this adventure Tree Trunks admits that she thought Finn was cute.
Mr. Pig makes another appearance in "Dream of Love" as Tree Trunks' lover. In this episode, it is revealed that he stays at Tree Trunks' house and is secretly in love with her. Tree Trunks calls him "Mr. Pig," which is when he got an official title. Mr. Pig confesses his love for Tree Trunks and she admits she loves him as well, which results in the two publicly displaying their affection for one another. The citizens of the candy kingdom become disgusted by their displays of affection, which resulted in Finn and Jake trying (unsuccessfully) to separate the two. In the episode, "Apple Wedding," she and Mr. Pig get married. She is seen wearing her wedding ring from him in her next appearances.
In "Escape from the Citadel," Tree Trunks nearly tells him she wants a divorce but when Finn and Jake leave the baby-fied Lich on her and Mr. Pig's doorstep. She declares "This changes everything!" as they are now a family.
Sweet Pig Trunks or "Sweet P" for short, is Tree Trunks and Mr. Pig's adopted son. Tree Trunks and Mr. Pig take great care to treat him with love and kindness, with Tree Trunks even performing a nightly "sweet" ritual to help Sweet P go to sleep. They frequently reassure him that his memories of being the Lich, which come to him in his sleep, are "just a dream." Sweet P has also provided well for his parents; the gold he acquired from the King of Ooo was used to greatly expand Tree Trunks and Mr. Pig's home. Even the King of Ooo refers to Tree Trunks and Mr. Pig as "loving parents," and they have helped Sweet P become a kind, generous being with little resemblance to his previous, undead existence.
Not much is about the nature of the relationship Tree Trunks has with her mother as they were not seen interacting. However, Mama Trunks is shown to approve of her daughter's marriage to Mr. Pig as it meant she was happy.
First appearing in "High Strangeness", Tree Trunks' alien husband visits her every so often to bring her to see their five alien-hybrid children on his planet. At first he thought she was just joking, and shrugged it off; especially after she told Mr. Pig that he held a special place to her. She refers to him as her husband when Mr. Pig demands to know who he is, suggesting Tree Trunks has been in a polygamous relationship with both the alien and Mr. Pig. Though Mr. Pig never seen giving her a answer or response, due to shock. They are still seen together during the Elements arc and Sweet P refers to them as a couple. Meaning Mr. Pig accepted Tree Trunks life style or may go along since her "husband" would not return for another 40 years.
Wyatt is one of Tree Trunks's ex-husbands, along with Randy and Danny. According to him, he had taught Tree Trunks to play tennis and she called him baby when she defeated him in a match. Their relationship had ended because Tree Trunks thought that he was "stifling her spirit." It was revealed how he'd continuing stealing her pies, so he could eat them, may have contributed. Wyatt appears to have gotten over Tree Trunks as he is seen making out with her mother Mama Trunks.
Tree Trunks and Ice King do not interact with each other until "Mystery Dungeon" where they work together, along with Neptr, the Earl of Lemongrab, and Shelby. Throughout the episode, she mispronounces his name "Ice Cream."
The first time Tree Trunks and Shelby interacted is in "Five More Short Graybles," where Tree Trunks mistakes Shelby for a middle finger. Tree Trunks and Shelby never closely interact with each other onscreen until "Mystery Dungeon" where they work together, along with Neptr, Earl of Lemongrab, and Ice King. Tree Trunks and Shelby may also know each other from Finn and Jake Movie Club in "Video Makers."
Earl of Lemongrab
Tree Trunks and Lemongrab never interact with each other until "Mystery Dungeon" where they work together, along with Neptr, Ice King, and Shelby. Throughout the episode, she mispronounces his name "Lemoncarb." She is apparently aware of the fact that there are two Lemongrabs.
Tree Trunks and Neptr never interact with each other until "Mystery Dungeon" where they work together, along with Ice King, Earl of Lemongrab, and Shelby. Throughout the episode, she mispronounces his name "Nectar." In "Be Sweet," she suggests to Mr. Pig that they hire Neptr instead of Lumpy Space Princess next time they need a babysitter.