Due to the fact that all the player characters are mostly Heroic Mimes in the main games and the spin-offs, some people occasionally characterize them as being The Speechless. They may use sign language as their main form of communication with others if this character trait is chosen for them. If you read the dialogue it's obvious the protagonist talks and is being replied to, it's just we're never shown it; and strangely enough, the most talkative one so far is Red, the same one known for being quiet. However, how much is mostly up to the player's imagination.
Red is stoic and quiet. Adaptation counterparts, official art, and in-game dialogue (particularly Copycat's dialogue and possibly Blue mocking you as a "chatty gossip") imply Red is a normal, even Hot-Blooded, kid, at least in the Kanto games. Red as the quiet stoic became Ascended Fanon as of Pokémon Sun and Moon and Pokémon Masters, where Blue now teases him for his newfound silence. To reconcile this, many fans portray Red as being peppy when he started his journey but have him become more stoic as he ages. There's another common interpretation that Red is hot-blooded but also deaf or mute.
In fanon, it's common for Sabrina to be depicted as intimidating or unapproachable when she's really just quiet or shy. This is related to other fanons that she later attempted to try and seem more approachable.
Thanks to her "rural" look, Lyra is often depicted as a tomboy, though not quite as tomboyish as May or Hilda. This is often used as a contrast to Ethan or Dawn.
Lyra is also portrayed as being very cheerful, ditzy, and naive. While this is canon with when she's an NPC, it's still common when she's portrayed as the player character in fics, partially to contrast Silver, and partially for amusement (mostly in regards to Silver constantly losing to someone that much of an antithesis) and/or shipping value.
Morty as The Stoner. Anyone ever wonder where all the smoke in his gym came from?
Erika being a case of Silk Hiding Steel, based on her mysterious expressions in her pre-battle art.
Roark having self-confidence issues and/or thinking he'll never be a great Gym Leader.
Cynthia is usually portrayed in raunchier materials as an overtly flirtatious MILF at best and a Memetic Molester at worst, especially towards the player character, due to her status as Ms. Fanservice and her canonic Cool Big Sis type of personality. At the same time, she's usually elevated to full-on Memetic Badass status thanks to her battles usually being some of the most difficult in the entire franchise.
Spark being a cute, dorky, sometimes somewhat stupid, Nice Guy in contrast to the fiery Candela and Emotionless Girl Blanche, is extremely popular.
Anime
Ash Ketchum, with a thousand plus episodes and decades of fandom developments behind him, gets plenty.
Ash can be portrayed as Obfuscating Stupidity, particularly when it comes to love. Other fics will just have him be more aware of these things by default, since if Ash retained his canon ignorance in shipping fics, the large majority of them would be impossible to write. The former is frequently paired with Daddy Issues that Ash in canon has never displayed, with Ash being aware of those attracted to him, but not pursuing it at first in fear that he'd become like his absentee father.
Ash as a Stepford Smiler is also quite common. Since he's been through a lot and seems to be exaggerating his joyful nature in recent times, writers headcanon that this is his way of coping with traumatic events such as his multiple deaths (or near death experiences). This is particularly common after the Team Flare conflict and is often a part of Alola fics.
Ash's status as having Seen It All, while not absent in canon, is played up a lot in fanfics. It is not uncommon to see Ash be more amazed by mundane things than the actions of in-universe deities and the fate of the universe.
Serena as a Covert Pervert with Single-Target Sexuality for Ash, taking her attraction to him from canon and dialing it up several notches. This emphasis on her interest in Ash in turn leads to Memetic Psychopath treatment aimed at those who might also be interested in Ash.
Her rival Miette is sometimes portrayed as a Fille Fatale with a lot of dating experience, to contrast Serena being The Ingenue. Also, while Miette in canon is all but said aloud to be pretending to be interested in Ash to screw with Serena and to encourage her to make a move, fanon Miette is more likely to actually have interest in Ash.
Mallow similarly is portrayed as rather horny and flirtatious in Lemons, due largely to her status as the Ms. Fanservice of the Alola Trio. When she's not, Lana's game and anime Covert Pervert attributes get turned up to eleven to be the horny flirt character of Alola instead, or at times alongside Mallow.
Goh being written as a Shrinking Violet with a supreme lack of confidence, so he can serve as the Uke in Yaoi fanfics. The real Goh is brash and overconfident, and if anything acts tsundere around Ash. He's not quite as vulnerable as commonly portrayed.
His First Friend Horace has an innocent and kind personality in canon, but it's possible to find him depicted as a flamboyant and flirtatious KidAnova in fanart and fanfics, likely because of his resemblance to certain characterswho act like that. Sometimes justified when he's portrayed as older.
