|Introduced in||"My Two Favorite People"|
|Latest appearance||"Mystery Dungeon"|
|Voiced by||Pendleton Ward|
Shelby made his first appearance in "My Two Favorite People" and later returns in "Video Makers." He can talk and lives in Jake's viola. He gave an idea to Jake, which is to spend more time with Finn and Lady Rainicorn at the same time. This leads to the events of "My Two Favorite People." He has the same tone of voice as Manfried. He also made a cameo appearance in "What Was Missing" when he crawled in and out of Jake's viola, and narrated the ending of "Holly Jolly Secrets Part II," where he and the general cast watched videos and wore sweaters. During the winter, he is known to wear a green sweater with two candy canes on it. He appears in "Five More Short Graybles" reading a book while sitting on a statue with a bat, and has a major role in "Mystery Dungeon."
It should be noted that Shelby appears as an earthworm, which is a hermaphrodite. However, he is a male as confirmed by Pen Ward. 
Finn and Shelby are friends. In the episode "Video Makers," Finn just described as "Shelby, the worm who lives in Jake's viola" as at they were beginning to become friends. Though in the episode "Mystery Dungeon" he actually talks to Finn as a friend.
Jake and Shelby are friends since he lives in Jake's viola. What also makes Shelby a good friend to Jake is that he gives advice to Jake in the episode "My Two Favorite People."
Shelby and Tree Trunks appear to be friends. In the episode "Five More Short Graybles," he said hello to her. In the episode "Mystery Dungeon," they appeared to be friends and had to work together alongside Ice King, Lemongrab, and Neptr.
Shelby never interacted with Lemongrab until "Mystery Dungeon" where they must work together alongside Tree Trunks, Ice King, and Neptr. However, they must be comfortable with each other because Shelby rides on his head for part of "Mystery Dungeon."
Shelby never interacted with Ice King until "Mystery Dungeon" where they must work together alongside Tree Trunks, Lemongrab, and Neptr. In general, he was annoyed by Ice King's myopia, desperation and selfishness, particularly when it was revealed Ice King had knocked the others out to be brought to the dungeon in an effort to get the Ancient Sleeping Magi of Life Giving to bring his Fionna and Cake fan-fiction to life (Shelby was particularly annoyed, as Ice King had planned to use him as fish bait, plus he would have brought something to be brought to life had he known). Later, as Finn and Jake watch Ice King and Neptr pretend Fionna is around in Ice King's Imagination Zone, Finn wonders if there's anyone sadder than the Ice King. Shelby responds with a dry, "Me, watching this."
Shelby never interacted with Neptr until "Mystery Dungeon" where they must work together alongside Tree Trunks, Ice King, and Lemongrab.
- My Two Favorite People
- Video Makers
- What Was Missing
- Holly Jolly Secrets Part I
- Holly Jolly Secrets Part II
- Five More Short Graybles
- Mystery Dungeon
As the picture shows, he is a worm. However, unlike the other worm characters, Shelby more closely resembles an earthworm in color and shape. He is the color pink and has black eyes.
- Pendleton Ward does the voice of Shelby and then it is computer generated for the show.
- Shelby was the answer to one of Gaia Online's ten trivia contests to answer to try to win a first season DVD set.