01 - Preheat oven to 375°F or set a large nonstick skillet over medium heat.
02 - Cut ghost shapes out of tortillas using a cookie cutter or sharp knife; expect 2 ghost cutouts per tortilla, for a total of 8 pieces.
03 - Arrange half of the tortilla ghost cutouts on a baking sheet lined with parchment paper, or on a plate if using a skillet.
04 - Distribute shredded mozzarella and cheddar cheese evenly over each base ghost. Scatter bell peppers or green onions if desired.
05 - Place the remaining tortilla ghosts over the filled bases, gently pressing to encase the cheese and fillings.
06 - Affix 2 olive slices onto the top layer of each quesadilla for eyes and 1 slice for the mouth. If preferred, slice olives into pieces to shape the mouth.
07 - Using a pastry brush, lightly coat the top of each quesadilla with melted butter or olive oil for a golden, crispy finish.
08 - Bake for 8 to 10 minutes, or until tortillas are crisp and cheese is thoroughly melted. As an alternative, cook in a skillet for 2 to 3 minutes per side, flipping with care.
09 - Remove from heat and allow quesadillas to cool briefly; serve them warm.