The Creep's face is a zombie-like mound of mud, his skull shape is very close to that of a turtle. The Creep would steal his wardrobe from a sunbeaten scarecrow, including his first mask. For his second mask he wears Casey's goalie mask. He has daisies growing on his skin.
Following his defeat at the hands of Shredder, Leonardo spends some time recovering in North Hampton, New York. Donatello concocts a batch of medicine using Mutagen as a base and feeds it to Leo in an attempt to aid his recovery. Leonardo vomits up the medicine into the shores of the bog, which mutates the vomited part into Creep. Creep stalks the Turtles, April, and Casey near the O'Neil Farmhouse. Raphael is the first to be targeted by Creep. Creep then ambushes Donatello and Michelangelo, near a shack that contains the bottle of the mutagen medicine and Raphael turned into a plant mutant.
Creep then attacks Casey and April as they try their best to take down Creep where it ends up taking Casey's hockey mask. Upon seeing April get abducted, Leonardo traces Creep to his shack where he ends up fighting it. After Leonardo walks back to the shack where the group is attacked by Creep, they try their best to take down Creep. Using the mutagen medicine bottle, the Turtles and April play keep away with it until Leo destroys the bottle and April and Casey manage to chain Creep. Donatello was able to use an I.V. vacuum to drain the mutagen out of Creep in order to restore Raphael from his flower form. The rest of Creep ended up back into it's goo-like form which starts to glow in a glass jar.
In The Creeping Doom, the creep returns and emerges using one of Donatello’s brain serums. It steals one of Snakeweed’s claws from Donnie's lab, which he used to grow a brand new Snakeweed, here dubbed "Son of Snakeweed". After being defeated by the turtles, the Creep's remains merge with Son of Snakeweed's, creating a new deadly creature: Creepweed.
The Creep is a super strong, super-durable mutant. He is capable of strategic planning despite his apparent limited intelligence. As a plant mutant, he is capable of regenerating any injuries inflicted on him. He can also reattach severed limbs, which he does with his left arm.
The Creep has the ability to transform other beings into feral, plantlike creatures, and syphon off their mutagen as nourishment. It is unknown if he has the ability to perform this on non-mutants, and if he could, whether he would receive any benefit from it.
The Creep's primary weapon is a pitchfork, but it is adept with other melee weapons such as katana.
- The Creep worships the mutagen as it's his life-giving source.
- The Creep is the second plant-like mutant with regenerative abilities to be introduced in the series, the first being Snakeweed.
- He appears to be inspired by Jason Voorhees from the Friday the 13th series as well as Man-Thing from Marvel Comics.
- His overalls have the brand name "Vorhees" as a reference to Jason, who also wore overalls.
- The Creep uses a bag with only one eyehole as a mask, but later he trades it for a hockey mask, much like Jason Voorhees.
- The shrine he has of the mutagen mirrors the shrine to the head of Jason's mother.
- Both the Creep and Jason Voorhees do not talk, only grunt.
- A sound effect similar to "ch ch ch ah ah ah" plays in the background for both of them.
- The Creep's theft of Raphael's mutagen and his temporary change in mutation depicted in Within the Woods, is a nod to Bloodsucker in the Mirage comic story arc Down to the River, River Hymn, and Old Man River.