Shuckle appears to be a small yellow turtle inside a red shell with many holes in it, fitting all four of its legs out. Some beige-like color surrounds the holes in Shuckle's body.
Shuckle has the abilities Sturdy and Gluttony along with the hidden ability Contrary. Sturdy protects Shuckle from one-hit KOs whilst Gluttony increases the healing restoration of Shuckle when it eats a berry. Finally, Contrary makes stat changes have opposite effects.
It is possible for Shuckle to have the highest attack of all the Pokémon using the move Power Trick which switches a Pokémon's Attack and Defense. The drawback on those tactics is his pretty low ATK value, peaking at 130, meaning that he can become pretty defenseless once he inverts ATK and DEF values.
Despite Pokédex Entries saying that Shuckle has weak muscles, Shuckle is able to learn Rock Smash and Strength possibly because of its hard defense shell.
Shuckle is the only dual-type Pokémon that can naturally have the ability Gluttony.
Shuckle appears to be based on a tortoise or a turtle whilst its names appear to be derived from shuck, barnacle or the word turtle.