Pull out your PSP with your GBA emulator homebrew installed (or even on your PS3 if you have it too)! This is one ROM that you do not want to pass up the opportunity of playing.
Back in 2007, @LinkAndZelda137 and @Z3IKKU (a previous -Hacks writer) began developing a complete remake of the game Pokemon Crystal from the Gameboy Colour using the "shell" of Pokemon Fire Red's graphics on the Gameboy Advance. After a long 5 years, in 2012 we can finally get our callused thumbs on one of the most flawless and incredibly well done pieces of "universal homebrew" (play it on your PC, PSP, PS3 whatever you want) that can be seen in a Pokemon remake.
I won't go into full detail about the game and what these dedicated developers have packed in, but you can most definitely read up on it all on the game website and what the vast expanses of this amazing Crystal Version re-do have to offer.
The game is also available for download on the site linked above, and you can read through the more recent development journal as more work is put into such an outstanding ROM. Many popular YouTubers have actually picked up the game doing Let's Play's of the game in speed runs, and even full playthrough's of the old beta's.
So download the game from the link above, get that emulator running and begin your pixelated journey through Liquid Crystal. You won't be disappointed.