The Wall of Flesh makes its first and only appearance in the episode "Tree Trunks," when it was stepped on by Finn, Jake, and Tree Trunks in its home in the Evil Forest. It soon rose up from the ground and barricaded their path. Finn and Jake began punching it with no effect while Tree Trunks, thinking that the Wall of Flesh needed some "tender love and care," put stickers on it: a rainbow, a scratch-and-sniff pickle, and a holographic unicorn (without a horn). The Wall of Flesh got angry and picked up Tree Trunks, preparing to eat her. Finn noticed what was going on and sliced off the Wall's arm, saving Tree Trunks. The Wall of Flesh melted and retreated into a tree while whimpering.
The Wall of Flesh is a pile of flesh that can form itself into a wall with a floor. It has two eyes, one next to its mouth and the other is on the part of the creature that is on the ground. It also has one mouth. It is peach-colored, like flesh.