Line a 9″ square or 11×8″ pan with waxed paper. Spray waxed paper with non-stick cooking spray and set aside. Melt butter in a large saucepan over medium heat. Add the marshmallows and turn heat down to medium low. Cook and stir till smooth and melted. Remove from heat and stir in vanilla. Add cereal and chopped Oreos, and stir till evenly coated. Press firmly into the prepared pan.
Remove from pan and cut out with a Mickey Mouse cookie cutter. Let sit for 3-4 minutes, then insert popsicle sticks if desired. Cool completely.
Melt chocolate chips and oil in a glass bowl in the microwave at half power. Stir every 30 seconds until smooth. Spoon melted chocolate over the Mickey ears, then place on parchment paper or waxed paper. Sprinkle with red sprinkles. Let sit till chocolate sets. It will take several hours, so plan ahead!
Notes
I used an 11″x8″ pan and got 12 treats. If you use a 9″ pan, your treats will be thicker, and you will get about 9.