Whisk together the flour, sugar, baking powder, baking soda and salt in a large bowl.
In a medium bowl, whisk together the buttermilk, melted butter, eggs and vanilla. Pour the buttermilk mixture into the flour, and stir until combined but still somewhat lumpy. Mix in 1/4 cup of the sprinkles.
Heat a large nonstick skillet or griddle pan over medium-high heat. When hot, lightly brush with oil, then reduce the heat to medium-low.
In batches, spoon 1/2 cup batter per pancake onto the skillet, and immediately sprinkle some of the remaining sprinkles. Cook until bubbles start to form on the surface of the pancakes, 2 to 3 minutes. Flip and continue cooking until golden brown on the underside and cooked through, 1 to 2 minutes more.
As you go, transfer cooked pancakes to a baking sheet, cover loosely with foil, and keep warm in the oven.
Heat the frosting in the microwave until just barely runny, about 40 seconds (do not overheat or the frosting will separate). Stir.
Make a giant pancake stack, and pour the warm frosting over the top. Sprinkle with additional sprinkles. Serve immediately.