Shellder

Shellder's hard shell repels any kind of attack, and Shellder is only vulnerable when its shell is open. In "The Evolution Solution," Professor Oak enlists the aid of fellow Poke-ologist, Professor Westwood (who programmed the Pokedex), to figure out the mystery of why, after a Shellder clamps onto a Slowpoke's tail, it becomes a Slowbro! Do you know why Shellder clamps onto Slowpoke's tail?

First appearance: Episode 70—"The Evolution Solution"