YOU CELEBRATE BECAUSE YOU JUST CAUGHT THE MOST POWERFUL POKEMON! (debatable if you compare it to Mew) Just migrate it to DS game and/or train it up.
If you still have some Pokemon to catch for your pokedex then I guess you can do that.
The elite 4s Pokemon grow by bout 11 levels you're suposed to battle them again
Yes, you can. But, You have to have caught Mewtwo already, beaten the Elite 4 12 times and given the Ruby and Sapphire to Celio. Next, you go to the spot where you caught Mewtwo in Cerulean Cave, walk/run around some and eventually Mew will appear.
Train your mewtwo it will learn aura sphere at lv 90-100
Have fun.
Use you masterball on suicune because its impossible to catch it without a masterball it would just flee i cuaght mewtwo with a great ball but make sure you have lots of them.
I don't think you can sorry :( Mewtwo; yet another legendary Pokemon that cannot be caught in Pokemon Ranger. Try as you may, it cannot be caught in that game.
you must beat the elite 4 twelve times go to where you caught mewtwo and catch mew :)
Go to where you caught mewtwo and pres a 500 times
Face the Pokemon League again
He battles team rocket, wins and goes to someplace else
Mewtwo cannot be caught in Pokemon Crystal, it must be traded in from Red, Blue, or Yellow through the Time Machine
to the top of mt.cornet where you caught dialga