13laze13oy, take a Squirtle and name him Koops.
This Squirtle manages to get his hands on your Pokédex, and decides to follow it blindly.
Fire Red Pokédex (Squirtle) said:
When it retracts its long neck into its shell, it squirts out water with vigorous force.
Following this, Koops must use Withdraw at least once before he can use any Water-type attacks.
In addition, after using Withdraw, he cannot switch out or run away, and can only use Water-type attacks or Withdraw.
He can never forget Withdraw.
To evolve, he must solo your rival twice.
Fire Red Pokédex (Wartortle) said:
This POKéMON is very popular as a pet. Its fur-covered tail is a symbol of its longevity.
As a Wartortle, Koops becomes obsessed with his "longevity", or long life.
If he is below 50% health, he can only switch out, use either Protect or Withdraw, or be healed.
In addition, if he has a status condition, he cannot fight until you return to a Pokémon center to heal.
However, this all changes once you enter Blaine's gym.
Koops decides to risk it, and must solo the entire gym, including Blaine.
All other restrictions are dropped, but he must use Withdraw immediately each time he is sent into battle, to protect himself.
He can evolve after this solo.
Fire Red Pokédex (Blastoise) said:
It crushes its foe under its heavy body to cause fainting. In a pinch, it will withdraw inside its shell.
As a Blastoise, Koops is proud of his newfound power.
He must learn either Skull Bash or Double-Edge, and can only use these two moves to KO foes.
If this restriction is broken, he must Withdraw on his next turn in battle. (Even if it's a different battle)
If his health is in the red, the only move he can use is Withdraw.
He must solo at least two Pokémon in the Elite Four.
Good luck!