Crust
Preheat the oven to 350º F.
Line a regular-sized muffin pan with 12 muffin liners.
In a mixing bowl, combine the oreo crumbs and melted butter until it resembles coarse sand.
Put 1-2 tbsp of oreo crumbs in each muffin cup.
Use a 1/3 cup (or similar) to press the oreo crumbs down firmly into the pan.
Bake the crust for 5 minutes. Remove from the oven and allow to cool while prepping the cheesecake.
Cheesecake
In a mixing bowl, beat the cream cheese with an electric mixer until smooth, about 2-3 minutes.
Beat in the sugar and vanilla extract until smooth.
Add eggs one at a time, mixing well after each addition.
Fold in oreo crumbs and larger oreo pieces with a spatula.
Place a little more than 2 tbsp of cheesecake batter in each muffin cup.
Optionally top the cheesecakes with additional oreo crumbs or pieces.
Bake for 15-17 minutes, or until the center is slightly jiggly.
Allow to cool to room temperature, then refrigerate for at least 2 hours before serving. If refrigerating overnight, cover loosely with plastic wrap.