Belle is presented with a glorious smorgasbord of food during her first night in the Beast's magical castle. Among the dishes served is the Grey Stuff, it’s delicious!
Disney released the recipe and it is a cookies and cream pudding mixture on top of a sugar cookie base. You start out with crushed Oreos, then add vanilla pudding, chocolate pudding, and whipped topping. All of that goes piped onto a cookie and is topped with crushed Oreos and sprinkles.
Growing up in Los Angeles in the 70s/80s we visited Disneyland on a regular basis and often after school, before "Annual Passes".