Koga

"Fwahahaha! A mere child like you dares to challenge me? The very idea make me shiver with mirth! Very well, I shall show you true terror as a ninja master. Poison brings steady doom. Sleep renders foes helpless. Despair to the creeping horror of -type POKéMON!"

- Koga, Pokémon FireRed and LeafGreen.

Koga (キョウ Kyō) served as the Gym Leader at the Fuchsia City Gym. Two years later, during the Generation II games, Koga became a member of the Elite Four and his daughter, Janine took over the gym and used poison Pokémon as well.

He specializes in Poison-type Pokémon, and as a Gym Leader gave out the Soul Badge for trainers that could defeat him.

Games
Koga first appeared in the Generation I games as the Fuchsia City Gym Leader. His gym was constructed with an array of invisible walls, fashioned into a maze. This forces the player to walk through the maze fighting Gym members, with the destination in the middle where Koga awaits.

Later, in the Generation II games, Koga has been promoted to Elite Four status. With the absence of a Gym Leader at Fuchsia Gym, Koga leaves the Gym under his daughter's care, Janine, making her the new Gym Leader.

In the remakes of the original games, Pokémon FireRed and LeafGreen, Koga is once again a Gym Leader, as it takes place during the same time period. The only difference is the level of his Weezing, and his updated appearance.

Season 1: Indigo League
Koga appeared in the episode The Ninja Poké-Showdown, where Ash and company stumble across his Gym. Not appearing until later in the episode, Ash can only find a plethora of hidden traps within the gym, and then later Koga's sister Aya. After the appearance of Koga, and a small incident with Team Rocket, Koga and Ash finally have their battle, uninterrupted.

The two have a one-on-one battle, with Ash using his Charmander, and Koga using his Golbat. Initially having some trouble, Charmander was unable to hit the Golbat, but after using Fire Spin, Ash was the victor. Upon leaving Koga rewarded Ash with the Soul Badge.

Red, Blue and Green Arc
In the Pokémon Adventures Koga is an executive for Team Rocket and along with Sabrina and Lt. Surge he fights Red to prevent him from interfering, but, as usual, this results in failure.

Gold, Silver and Crystal Arc
It was shown that he has a daughter who worried about him because he wasn't seen for a long time.

Gym Leader Castle
Gym Leader Castle Round 2

Voice actors

 * English: Stan Hart
 * Japanese: Hōchū Ōtsuka
 * Polish: Radosław Popłonikowski
 * Spanish: Juan Fernandez
 * Iberian Spanish: Gerardo Vasquez

Trivia
In a Pokémon card related to Koga, called Koga's Ninja Trick, there is a symbol that looks similar to a Swastika. However, it is actually totally different, in positioning and in meaning. A Swastika is in a diamond angle, and the points on it point clockwise; the symbol depicted on the card was in a square angle, and the points were counter clockwise. The symbol on the card was of a different culture and was many years before the Nazi Party, and meant "peace". When the card was released in the U.S., it was changed to a different symbol.