Once upon a time I was Masuda method breeding for a shiny snivy. I decided to start hatching magikarps because they are faster and gyarados is cooler in my opinion. I had a snivy egg containing a shiny snivy in my PC boxes. I hatched 650 magikarps no shiny. Then, I tried chespins (I love chespin and he is more pleasing to look at then a flipping red karp) I hatched over 1000, no shiny. I later decided to hatch leftover eggs I had in my PC boxes(from when I wanted to breed something else but I had to claim the egg from the lady) and the first egg was a shiny contrary snivy (brave, sadly). I was happy, but mad at the same time because I wanted a shiny chespin not a snivy. But, I had that snivy sitting in my PC the entire time I hatched the 1650+ eggs. Was that the reason I got no shiny? Please, include a source (mabye someone saying they hatched a shiny with a shiny egg sitting in their PC boxes)
I had a shiny charm, and was breeding a Japanese ditto with my magikarp and chesnaught that I caught myself.