Giovanni

 

First Series of Games (Red/Blue/Yellow, FireRed/LeafGreen)

 

Celadon City

Giovanni is the main villain of the first generation of Pokemon games ( Red/Blue, Yellow, FireRed/LeafGreen) . He is the leader of Team Rocket, which the player first finds out in the basement of the Game Corner in Celadon City. There it is revealed that the Game Corner is actually the base of operations for Team Rocket in the Kanto region. His team of Pokemon in the hideout is Onix, Rhyhorn, and Kangaskhan.
 

Saffron City

Later in the game, when the player arrives at Saffron City (or even before, because all entrances are blocked), the player finds out that Saffron is under the control of Team Rocket. Giovanni is on the top floor, holding the head of Silph Co. hostage. After defeating him there, he will disappear, along with the rest of Team Rocket. For his team, he drops his Onix, and replaces them with Nidorino and Nidorina
 

Viridian City

When the player gets to Viridian City to collect the last Gym Badge (The Earth Badge), it is revealed that Giovanni is the leader of Viridian Gym, and was using it as another Team Rocket Base. (Also he is the only gym leader fought multiple times) The gym is designed like the Rocket Hideout, with slide tiles and teleporters. When you defeat him, you will receive the Earth Badge and the Fissure TM (In FireRed/LeafGreen, the Earthquake TM), and he states that this is the end of Team Rocket, and will disappear. He drops Kangaskhan to add Dugtrio and another Rhyhorn, while his first Rhyhorn, Nidorina, and Nidorino evolved into Rhydon, Nidoqueen, and Nidoking respectively.
 
Note: In the Yellow version, his team is slightly modified, mainly due to the addition of Persian, like the one his TV counterpart owns.
 

Second Series of Games (Silver/Gold/Crystal, HeartGold/SoulSilver)

In the original second series, Giovanni is replaced by the rival of the first series as the gym leader of  Viridian City.  When Team Rocket takes over the Radio Tower in Goldenrod City, it is revealed that the whole plan was to call out to Giovanni to tell him that Team Rocket has been reformed and that they are waiting for him to come back and take over. They are disbanded again by the player, and that is the definite end of Team Rocket.
 
In HeartGold/SoulSilver there is a special event when you download a Celebi from WFC. Celebi will take you back in time, where it is revealed that Giovanni is the father of Silver, the rival in this set of games. Silver has nothing but resentment for Giovanni, which explains his attitude towards Team Rocket (how they are a pathetic bunch of cowards.
 

At the end of the event, you will find Giovanni in the Tohjo Falls, there it is revealed that he has been training since his defeat at the hands of the the protagonist of the first games. He has a radio inside the cave he is training in, so he does hear Team Rocket calling out to him, but they are defeated and disbanded before he can return. His team consists of his signature Nidoking and Nidoqueen, along with Kangaskhan and Honchkrow.
 

Appearances in other games

Pokemon Puzzle League

  Giovanni appears in Pokemon Puzzle League as the holder of the Earth Badge. He also claims to be the Puzzle Champion when you first fight him. His team is similar to his team from Yellow, with a Persian and a Nidoking, but he also has a Sandslash. He is also the final boss of the Spa Service Mode, where the story mode is Ash fighting Team Rocket. Along with everyone else in the game, Giovanni is based off of his anime counterpart.
 
 

Pokemon Stadium

Giovanni is the holder of the Earth Badge in the Gym Leader Castle in Pokemon Stadium. His team is similar to the team in Yellow. Persian, Nidoqueen, Nidoking, Tauros, Rhydon, and Dugtrio. The second time you battle him, he drops his Dugtrio and Rhydon for Moltres and Gengar.