Player character

A player character (Norwegian: Spiller karakter) in the world of Pokémon is the main character in the plot of the Pokémon games. Remarkably silent, players are represented by an avatar; it is left up to the real player to "fill in" what they imagine the character is feeling, thinking, and acting, thus immersing him/her within the world of the game.

Gameplay
In the core series games, the player characters are Pokémon Trainers beginning their Pokémon journey. They start their journey in their hometown by getting a starter Pokémon, a Pokémon that appears very early in their native region's Pokédex, and is usually of the Grass-, Fire-, or Water-type. The region's resident Pokémon Professor will always give them this, as well as a Pokédex. Starting in Pokémon Crystal, players can also choose their character's gender. Usually, they have rivals who begin their journey at about the same time. Players take part in several events, and meet a great number of Pokémon and people during their adventure. A common target is to conquer a Pokémon League's eight Gym Leaders and Elite Four, and become the Champion. Several additional side-quests occur during and after each game's main plot.

To date, only one player character has reappeared from an older generation in a role other than that of the player. In Generation II and the Generation IV remakes, when Ethan or Kris/Lyra travels to Mt. Silver and reaches the deepest point of the cave, Red is found, utterly silent as he was under the player's control. At the time of these games' respective releases, Red's Pikachu was the highest-leveled Pokémon owned by an in-game Trainer (Barry's fully evolved starter Pokémon temporarily surpassed the standard set in Gold and Silver until the release of their remakes, HeartGold and SoulSilver). Red reappeared in Black 2 and White 2, in the Champions Tournament of the Pokémon World Tournament, and again in the Alola-based Generation VII games, as the leader of the Battle Tree with Blue.

The player character can be named in all core series games at the beginning of the game using the same interface as that for entering nicknames for Pokémon.

In the main series
In the Pokémon anime, six of the player characters have been given major roles, four of them in the main series. Ash represents Red (his game counterpart), being based on him in appearance as well as basic history (Ritchie, by extension of resembling Ash, also resembles Red, although his basic history is unknown).

At the beginning of the Advanced Generation series, May was introduced in order to better represent Generation III, as both Misty and Brock are characters who originated in Generation I. Likewise, at the beginning of the Diamond & Pearl series, Dawn joined Ash. In the XY series, Serena joined Ash in order to represent Generation VI.

Jimmy and Marina appeared in The Legend of Thunder! special, taking a similar role to Ash and his companions, fighting Team Rocket members to protect Legendary Pokémon. While the protagonists of Generation II did not join Ash's company, these two filled the roles as the anime counterparts to Ethan and Kris.

Lyra appeared in An Egg Scramble!, and joined the group for a brief time until Bagged Then Tagged!.

Ash and his friends have also encountered several player characters from the side games. Todd Snap was the first, and a special case, as he originated in the anime before appearing in Pokémon Snap. He joins the group for a few episodes at two points in the anime: once during the Indigo League and once during Johto League Champions. The others, Solana, Kellyn, and Ben are all Pokémon Rangers that Ash and friends assisted in rescuing and protecting Pokémon.

So far, Brendan has only made a few select cameo appearances at the beginning of some of the movies, while Lucas made a cameo at the beginning of Giratina and the Sky Warrior, where he was battling Brendan. Ethan also appears with a second counterpart at the beginning of Zoroark: Master of Illusions.

None of the Generation V and Generation VII player characters have yet been seen in the main anime.

In Pokémon Origins
Red has a direct counterpart as the main character in Pokémon Origins.

In Pokémon Generations
Direct counterparts of Red, Ethan, Brendan, Hilbert, and Calem appeared in Pokémon Generations.

Much like Red, none of the other player characters depicted in the miniseries have any lines of dialogue.

In the Pokémon Black Version 2 and Pokémon White Version 2 Animated Trailer
Nate and Rosa both appear in the animated trailer for Pokémon Black and White 2.

In the Pokémon Omega Ruby and Pokémon Alpha Sapphire Animated Trailer
Brendan and May both appear in the animated trailer for Pokémon Omega Ruby and Alpha Sapphire.

Trivia

 * Most of the male characters that Ash, the main character from the Pokémon anime, has encountered have been from side games, like Pokémon Ranger. The only counterpart of a male player character who has met Ash is Ethan, in the thirteenth movie.
 * Red's dialogue during his appearance as an NPC reflects the games' player characters' status as silent protagonists.
 * The list of default names per gender generally repeats from game to game, starting in Pokémon Crystal. Exceptions to this are character-specific names, which are names unique to a character and are usually references to the title or aspects of the game.
 * Until Generation V, the given Japanese names of the male player characters in the core series games (as NPCs) all end in ki (キ). This excludes Red's appearance in Generations II and IV, as he is not a player character during the games when he is an NPC. Inclusively, Lunick's Japanese name also ends in ki.