Because I have a shiny and foreign Ditto and I'm thinking of breeding it with my Shiny Metagross.
If the parents are shiny it doesn't make a difference however having both parents as foreign Pokemon does increase the chance.
It's called the Masuda Method, if my recollection is accurate.
How to do the Masuda Method
A parent's shininess has no affect whatsoever on the offspring
However, if the parents originate from different countries (A game with a different language I suppose), the chance of obtaining a shiny Pokemon increases - known as the Masuda Method.