When making chocolate molds -- like Easter Bunnies -- why does the chocolate turn white?

Depending on the chocolate you're using I'm guessing it's the fat separating from all the other ingredients and coming to the top, nothing to worry about though!

Mmmmmm... chocolate!

Its just the fats separating if you use a high coca mass chocolate and don't over work it this shouldn't happen but once the chocolate has been melted for some time and re worked it does tend to separate.