The Gameboy Advance systems can interact with games that are a different language. That is why people can freely trade between English versions of Ruby/Sapphire and Japanese versions of Fire Red/Leaf Green. However, the Gamecube is not compatible with other languages. Anytime the Gamecube is involved, you have to use equipment that uses the same language as the Gamecube. So, that is why you can't transfer a Jirachi from an English preorder disc to a German version of Ruby/Sapphire. UK versions may be compatible with a US Gamecube, since they use English, just as the US versions do, but I am not sure.