The Turtwig species can be found living in forests, much like other grass Pokémon. Many of them probably live with Professor Rowan, as he gives them out to new trainers . Like most Pokémon, Turtwig can eat berries, but being a plant Pokémon, he also goes through photosynthesis.
Turtwig appeared as a trophy in Super Smash Bros. Brawl along with the other starter Pokémon in the game (Piplup appeared as a Poké Ball Pokémon in addition to being a trophy). The following is Turtwig's trophy description:
"A Tiny Leaf Pokemon. Despite its animal appearance, Turtwig actually has vegetation sprouting from its head. The shell on its back is made of soil and hardens when it drinks water. Much like a plant, Turtwig performs photosynthesis, absorbing sunlight and making oxygen. It also relies heavily on water to keep its plant healthy and thus spends a lot of time near lakes."
In the anime
Turtwig first appeared in the made for TV movie Pokémon Diamond and Pearl, which was in a way a preview for the upcoming television show. In the movie, Turtwig appeared along side the other starter Pokémon Chimchar and Piplup.
Turtwig is the second Pokémon that Ash catches in Sinnoh. In the episode where Ash catches him, Team Rocket kidnaps Ash's Pikachu. Soon after they escaped in their balloon, it crashed. Noticing that the Pikachu was in trouble, Turtwig defended him against the team. Once Ash arrived, Turtwig thought falsely that they were trying to capture Pikachu, so Turtwig grabbed the tired Pokémon and ran. Later on, the misunderstandings were forgiven, and at the end of the show, Turtwig joins Ash's team.
In episode 6 of Diamond and Pearl, Ash's Turtwig battled with Paul's Chimchar, but lost.
In the manga, the character Diamond has a Turtwig.
Pokémon Trading Card Game
Currently there are three Turtwig cards available in the Pokémon Trading Card Game. In March 2007, Pokémon USA released a limited edition collectors level 10 Turtwig card along with their partner starter Pokémon (Chimchar Lv. 8 and Piplup Lv. 9).
Diamond & Pearl, as Turtwig Lv. 10, Grass-type common card.