Mew and Celebi
UPDATE (05/27/03): Mew can be caught in the game through using a code, otherwise a glitch in the game, go here for the complete details:
Mew and Celebi are probably the most talked about Pokemon. And probably one of the most popular questions relate to them: Where can I find Mew/Celebi? The answer is, you can't. Except for Mew, which there is a special code/glitch you can do (read above's UPDATE). There are many false rumors out there. Don't listen to any false rumors such as fight the Elite 4 1000 times or capture all 150 or 250 Pokemon, its false. Mew and Celebi can not be captured in the game through those ways (again, except for that special code for Mew). There are a few ways to get either a Mew or Celebi. You can get Mew or Celebi through a Nintendo promotion. Mew promotions are very rare. In the year 2001, they gave out Celebi at some Six Flags theme parks, as well as some other promotions, such as a contest. Pokemon Center has been known to give out Celebi as well. The other way is to use a cheating device, such as GameShark, to get Mew or Celebi (warning: using GameShark may cause harm to your game, use at your own risk).