Well, you can change the names in the PAL version of the results screen (or so I heard).
The US Brawl has the names in a file called "main.dol" or something.
^ this
it requires hexing, which. hexing the screen names is quite easy, the only sucky part is you cant have the name longer than the original characters name.
i think this is what ds22 said, idk i had it on a text document...
In order to change Jiggz result name, open up main.dol in a hex editor and search for 'Jigglypuff', which should take you to a section with most of the result names (be aware that the size of the name has to stay the same size, so Jigglypuff, being 10 characters, being replaced with a 10 character name or less with spaces to fill the remaining spots).
main.dol (the file you will be hexing) goes in the root of your brawl files folder (Ex: Gecko = private folder, Riivolution = going to have to be have an edited xml, which is what i did)
good luck.