18

18 is a Pokémon that usually every three days shifts to a different Pokémon of a different type. It is unknown why this happens, but it may be related to a scientific exploit. She will change form immediately if the body she is currently using is killed, and that form will be revived when it is cycled back to once more. No matter what form, she is a female.

Corsola
Corsola is the Rock-type. She is vain and often does not like the company of others. Her pastimes include traveling and making the most of each day.

Cacturne
Cacturne is the Dark-type. She works as a hired mercenary to whoever wants her, but due to not being around often she has trouble finding work. So she's resorted to killing just for the heck of it.

Togekiss
Togekiss is the Flying-type. She adores giving Pokémon who can't fly the chance to experience it. Very friendly and not that strong.

Druddigon
Druddigon is the Dragon-type. Along with her body comes an outfit modeled after Pretty Cure. Because of how embarrasing she finds it, she has low self-esteem and barely any strength despite the muscular dragon-y figure she has.

Magnezone
Magnezone is the Steel-type. It is a typical robot, and speaks in the first person. Attracted to metals.

Grumpig
Grumpig is the Psychic-type. She is an intelligent and strong Pokémon, who likes to travel and spar with passers-by.

Magcargo
Magcargo is the Fire-type. She is constantly depressed due to her lack of a body and destructive lava skin. She has attempted to kill herself multiple times but is baffled to find that she never really dies.

Krokorok
Krokorok is the Ground-type. A vulgar, conceited "croc", her sharp tongued remarks are not well-recieved by anybody.

Garbodor
Garbodor is the Poison-type. She's aware of her filth but still tries to make friends despite it. She also has a crippling problem with creating short-term memory.

Shedinja
Shedinja is the Ghost-type. It doesn't talk much but knows where it can be safely due to its Wonder Guard. It is strong but does not like to fight.

Timburr
Timburr is the Fighting-type. She is similar to Grumpig in traveling and sparring, but not nearly as smart. She'll dutifully respect anybody who bests her.

Vanillite
Vanillite is the Ice-type. She likes to make ice, snow, and cold puns. Whether they're good or not depends on who's listening.

Chansey
Chansey is the Normal-type. She adores children and will kindly give her eggs to anybody who wants or needs it. She doesn't like scary things.

Maractus
Maractus is the Grass-type. She's an expert dancer and dance teacher, having helped a few other Grass-types with their Petal Dances.

Ledian
Ledian is the Bug-type. She's one of the strongest Ledian in the world, but knows that her strength is nothing compared to a lot of other Pokémon. She speaks in a down-to-earth manner.

Quagsire
Quagsire is the Water-type. She is extremely dim-witted and likes kissing boys. This somehow attracted Bing to her.

Ampharos
Ampharos is the Electric-type. She has a crippling fear of predatory men and sees herself as a target. She also longs for the family that she believes she has somewhere. She once partially witnessed her transformation into Corsola.

Fairy-type
This one is yet to be determined, and will be if the account is ever revived.

Trivia

 * 17 was made on October 21, 2012. At the end of January 2013, her average tweets per day were around 13.
 * Since her creation, 17 has gained an average of 1.6 followers per day.
 * Her handle refers to her own identity. Shockingly, nobody else had used it yet.