cacth it

evolve it from a quilava!

Snag his Quilava. You can incounter him in three places;
Pethnic City
Shadow Pokemon Lab
Team Snagem Hideout

You can get it early in the game in Phenac City after you beat everyone
from Cipher. There will be 3 people guarding all exits from Phenac City.
All of them are Peons I think. There will be a blue one at the front
entrence where you rescued the girl, a green one on the left side of the
city, and the red guy will be on the right side of the city and he will
have a Quilava at Lvl 30 also with a Grimer as well. The green one has
Bayleef, and the blue one has a Croconaw. There all at Lvl 30.

You can either catch it in Phenac city from the Red Cipher Peon guy, snag it from the trainer later in the game, or trade it from another game once you beat the game. =P

In order to find the mythical bird you must first satisfy 3 conditions:
1. Catch all pokemon and fully purify all 48 Shadow Pokemon in story mode.
2. Beat all 100 trainers on Mt. Battle in "Story mode".And go to "Battle mode" beat 100 trainer on Mt.battle again.This can be done in either Single Battle or Double Battle mode. "I think beat single Battle is more faster"
3. After beating the 100th trainer on Mt. Battle in "Battle mode", Ho-oh will show up and will automactically be transported to your PC.
NOTE: If your PC is full, you will not get Ho-oh and must retry the Mt. Battle challange.

so you can have any pokemon

First you go to the city with all the water around it and go to the mayors there will be
people there beat and cauthch the shadow pokemon and then go to the red guy blocking the
right way out of the city battle him and snag his quilava and keep battling till it's
ready to open it heart prufy it and keep training till level 38 then it will evolve into
typhlosion