|As he appears in Goop's World 3: Shifted|
|Number of Games||7/8|
- "Mayonnaise! Mayonnaise!"
Shelldon makes his debut appearance in Goop's World, kidnapping Blossom to help King Grex attempt to rule the world. He and Moki are eventually defeated by Goop. He is one of the main villains of almost every Goop's World series game.
Shelldon's name comes from the common name Sheldon, combined with the word shell.
Shelldon is a bumbling idiot, similar in IQ to a toothpick, according to his boss King Grex. He doesn't seem to have any real evil tendencies, unlike his partner-in-crime Moki. He serves the purpose of a lovable oaf who is constantly blamed for all of Grex's failures (mostly by Moki). Shelldon has no real grudge against Gooptars in general or Goop specifically. He constantly forgets about his own strength, causing him to accidentally deal damage to Moki.
Shelldon has no real special abilities to speak of, aside from building large machines to use against Goop.
In Goop GP, Shelldon can tuck inside his kart and spinning down the track, spinning out any opponents he hits.
In Goop's World 3: Shifted, Shelldon is given the ability to shape-shift by the Shift Sprites. He and Moki both use this power in Goop's Big Game Land, but they screw up, causing them to fuse together into Shellki, an enormous Moki/Shelldon hybrid.
A year after Goop arrives in the Gooptar Kingdom, Moki and Shelldon sneak into Blossom's Castle on Blossom's birthday, kidnap her, and steal her collection of Magic Opals for their master, King Grex. Goop then sets off to stop him. During the final battle, King Grex first watches the fight from the air while Moki and Shelldon fight Goop in the A.G.A.M.. After the ending credits, they are shown exiting the ruins of the castle before a large statue of King Grex falls on top of them.
One year later, King Grex, now a ghost, tears apart the Ethereal Veil, the plane seperating the Real World and the Spirit World. This causes the two realms to mash together, creating a Real World/Spirit World hybrid and transforming all of the characters into monstrous versions of themselves. When King Grex is defeated, Moki and Shelldon are shown bedding down for the night in the old ruins of Castle Grex.
Two years later, King Grex prepares to attack the Gooptar Kingdom with his army, only to have his army be attacked by an even more powerful army controlled by Dr. Oktor Von Derwiff. For the common good, Grex and Frogrump agree to temporarily team up with Goop, Bing, and Tawnya. Moki and Shelldon stay behind to watch after Castle Grex's ruins.
Two years after the events of Opal HQ, King Grex, now inhabiting a robotic body built by Moki & Shelldon, returns once more to exact revenge. He figures out that Goop's shape-shifting powers are why he keeps losing, so he enslaves a race of fairies called Shift Sprites, who have the ability to transform themselves and anybody else into anything. He then uses these new powers on his Minions. In Goop's Big Game Land, an amalgam of landmarks from previous Goop levels, Moki and Shelldon attempt to use their newly-found shape-shifting powers at the same time, causing them to fuse together into an enormous creature called Shellki.
Sometimes after Shifted, King Grex finds his army once again under attack by Dr. Derwiff, who has escaped The Vortex. King Grex sends his new recruits (Chomper, Chucky, Snerlin, and Springear) to defeat him. Moki and Shelldon serve as the Mission Control of the Minion Brigade.
- In the original draft of Goop's World, Shelldon was the name of the Torto enemy.
- Shelldon's signature color is Navy Blue.
- Shelldon appears in the Toshiko-developed crossover brawler, Toshiko Crash-Up, as a Minion for King Grex.
- Goop GP is the only game where Shelldon has no English lines.
- Bing: Powered-Up is the only game in which Shelldon does not appear.
- In Goop's World 2: Paranoia, Shelldon is transformed into a "wereturtle".