Mix wet ingredients: in a large bowl, beat two eggs. Add milk and sour cream (or milk and yogurt, or buttermilk). Add butter and bacon fat. Add 1/4 tsp cinnamon and vanilla. Mix well with a whisk.
Mix dry ingredients: In a medium bowl, whisk together flour, baking powder, baking soda, salt, and sugar.
Add dry ingredients to wet slowly, whisking to combine. Do not overmix. Wet and dry ingredients should be fully incorporated, but small pockets of flour are fine.
Heat griddle to 350F or pan over medium heat. Coat lightly with bacon grease (or butter). Use a 1/4 cup measure to portion out pancakes, with each batch small enough that the batter circles don't touch.
Add several pieces each of cooked bacon and apples to each pancake immediately after pouring batter onto pan. It's important to add while the batter is still wet.
Watch for small bubbles to start to form on top of the pancakes. Flip with a spatula when bubbles are present and down side is golden brown, about 3 minutes. Do not push down on pancakes with spatula once flipped.
Cook pancakes an additional 2-3 minutes, or until second side is golden brown. You may hold cooked pancakes in a 200F oven while making additional batches. Coat pan with additional bacon fat before each batch.
Serve pancakes with butter, real maple syrup, and a fried egg.