Turtwig, the Tiny Leaf Pokémon. Its shell is made of earth and when it absorbs water, it becomes harder.
– Ash’s Pokedex
Turtwig is Gen IV’s Grass starter. It’s been featured quite a lot in the anime. Ash had a Turtwig (it evolved into Torterra), and so did his rival Paul (his Turtwig also evolved into Torterra). The gym leader Gardenia has a Turtwig, which she used in her battle with Ash. It defeated Ash’s Staravia (because in the anime, typing isn’t all that important) but lost to Ash’s Turtwig.
Turtwig evolves the latest of all starters, at level 18 (tied with Totodile). Despite being Grass type, it learns a Water type move by level-up, Withdraw, probably because it’s based on a turtle. Withdraw doesn’t seem very Water-themed to me, but is probably Water type because it was learned by Water types when it was introduced in Gen I.
Stat-wise, Turtwig has Attack as its best stat, decent Defenses, and is slow (since it’s a turtle)