The Crystal Gem Apple!!

Synopsis
Tree Trunks joins Fionna and Cake on an adventure through the Evil Forest in search for the legendary Crystal Gem Apple.

Plot
Fionna and Cake are playing with swords when Tree Trunks the elephant invites them into his house to have some of his apple pie. The first pie is touched by a fly, so Tree Trunks throws it away and makes another pie. As Fionna and Cake eat the pie, Tree Trunks asks them what they would do if they could do anything. Fionna says that she would go into space to fight space monsters, and Cake would carve her face onto the moon. Tree Trunks says he wants to pick an apple, but it is known as the rare Crystal Gem Apple. It is located in the Evil Forest, and Fionna and Cake decide to make his 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, he begins putting stickers on it. The Wall of Flesh flees when Fionna cuts off one of its arms, and soon Tree Trunks walks away, following a Skeleton Butterfly. He is attacked by Sign Zombies and begins having a tea party with them, not knowing they want to kill him. Fionna and Cake fight off the Sign Zombies and continue their adventure, until they encounter a Brain Beast. Fionna goes to fight it, but Tree Trunks' "adventurer's instincts" tell him to put on makeup and seduce the Brain Beast with his charms. Cake has to leap in to save Tree Trunks while Fionna attacks the monster's magic gem weak spot.

Fionna yells at Tree Trunks for putting himself in danger, and he leaves in tears, only to find the Crystal Gem Apple growing inside a mushroom-shaped tree. Unfortunately, a Crystal Guardian appears and begins copying Fionna and Cake's actions, blocking every attempt to fight it physically. As Tree Trunks is picking a mushroom, a Skeleton Butterfly appears with a keytar and plays music. As Tree Trunks dances with the butterfly, the Crystal Guardian begins copying her. Noticing this, Fioann and Cake try to fight it while it's distracted, but the Crystal Guardian is able to copy them all simultaneously.

The two adventurers realize that they have to fight the monster "Tree Trunks-style." They put on makeup and trick the monster into letting Tree Trunks take a bite of the Crystal Gem Apple. He bites the apple, pauses for a second, then explodes, leaving Fionna, Cake, and the Crystal Guardian shocked, and staring at each other in horror. In a final enigmatic scene, Tree Trunks is seen walking in front of a crystal background.

Major characters

 * Fionna
 * Cake
 * Tree Trunks

Minor characters

 * Wall of Flesh
 * Crystal Guardian
 * Brain Beast
 * Sign Zombies
 * Skeleton Butterflies
 * Worms
 * Snail
 * Flies