Bold indicates a Pokémon gains STAB from this move. Italics indicates a Pokémon whose evolution or alternate form receives STAB from this move. A dash (−) indicates a Pokémon cannot learn the move by the designated method. An empty cell indicates a Pokémon that is unavailable in that game/generation.
Dwebble jumps out of its shell and its whole body glows white and crimson red cracks form around its entire body. The white energy then breaks apart and comes off Dwebble's body like pieces of a shell. When the energy cracks and breaks apart, Dwebble's body glows crimson red. When Dwebble uses another attack right after using Shell Smash, the white energy particles floating around Dwebble will morph with the attack, giving it more attack power.
Crustle jumps out of its shell and its entire body glows white. Crimson cracks then form all around its body, and the white energy breaks apart and comes off Crustle's body like pieces of a shell. When the energy cracks and breaks apart, Crustle's body glows crimson red. When Crustle uses another attack after using Shell Smash, the white energy particles floating around Crustle will morph with the attack, giving it more attack power. Crustle's body continues to glow crimson until the battle is over as well.
Shell Smash is the only status move that affects more than three stats at once, and the only move of any kind to do so reliably. Only the attack AncientPower and its variations have a small chance of affecting an equal number of stats.
Shell Smash causes the greatest overall base stat changes of any move from no changes at all, with 8.
However, Belly Drum surpasses this if the user has a -3 stat change in Attack, resulting in a +9 net stat change, and capping at +12 if executed from -6.
With the exception of Gorebyss, all the Pokémon that are able to know Shell Smash have Defense as their highest stat.
Shell Smash is similar to Weak Armor, as both of them lower the Defense stat, but at the same time boost the Speed stat.