S1E35 : The Legend of Dratini

Ash and his friends get challenged by Team Rocket in seeing who can capture the most Pokémon within the Safari Zone, with Ash catching a whole herd of Tauros. As soon as Ash and his friends head out Pokémon hunting, Team Rocket manages to get the drop on the game warden (Mr. Kaiza) and forces him into giving up the location on where Dratini is (the Dragon Valley). In the end, Ash, his friends, Team Rocket, and Kaiza end up seeing the legendary Dratini and Dragonair, with the heroes saving the day.