Spray a skillet with cooking spray and heat over medium. Slice mushrooms and chop onion.
Add veggies to hot skillet and sauté until tender, approximately 6-8 minutes. Remove from skillet and set aside.
Whisk eggs and add to the same skillet. Cook, stirring gently until completely set, then remove from heat.
Place 1 tortilla in a separate large, nonstick skillet. Top with one slice ham, 1/4 eggs, 1/4 veggie mixture, 1 tablespoon mozzarella, 1 tablespoon cheddar, and another tortilla.
Cook over medium heat for 1-2 minutes per side until lightly browned and cheeses begin to melt; remove from skillet and set aside on a plate. Repeat with remaining ingredients until all have been used.
Once quesadillas are finished cooking, cut peppers into shapes and place on top to form a smiley face or other fun picture.
Serve with remaining bell pepper pieces and watermelon on the side.