This might be true for other Pokemon, but not for Ditto.
I caught my Shiny Ditto on Gold. I can't remember where. I totally flipped out. After pumping him up with the max amounts Calcium, Carbos, Iron, Protein and Zinc he would take and raising him to Lv 100, I decided to breed him.
I knew that the shiny gene didn't get passed on when breeding other Shinies, but this was Ditto. So, I bread my Shiny Ditto with a "normal" pokemon? I was flipped out to the max when I saw the results. The offspring was Shiny! I thought this must have been a glitch and tried again with another "normal" Pokemon and once again the offspring was Shiny. Needless to say I went on a breeding spree.
I'm still on the hunt to find me a Shiny Ditto on FR/LG.