Jeez... You can too catch the Legendary Dogs without a Master Ball, it's the same idea as any other Legendary. After you encounter and weaken them a few times (they don't heal if they flee), they won't run away as early. However, if you have a Mean Looker or a Spider Webber on your team, that will speed up the process. It's the same drill - inflict them with a status condition, and if possible, get them into the red zone. Then, just use the Ultra Ballz (they should take that word off the filter for the Pokemon games) you were going to use on Mewtwo and soon enough, you'll have a Legendary Dog and you'll be free to use your Master Ball on Mewtwo!
P.S. Did you notice? Whatever Dog you find will have a type that is super-effective against your starter.
Pan is back... for the fourth time. So sue me, I take frequent vacations. [color=red]If anyone wants to put a video game soundtrack on their iPod or something, this site is the place to do it>>
http://gh.ffshrine.org?r=35693