In a medium bowl, mix the mashed potatoes, egg, flour, cheddar, bacon bits, and sliced scallion until evenly combined.
Pour the panko onto a plate. Scoop ⅓-cup portions of the potato mixture, shape into ½-inch-thick patties, and coat both sides in panko. Place on a parchment-lined plate.
Freeze the breaded patties for 10–15 minutes — until firm enough to handle without bending.
Preheat the air fryer to 380°F (190°C) for 3 minutes. Spritz the basket with oil. Place the patties in a single layer, leaving space between each, and spritz the tops with oil.
Air fry at 380°F for 12–15 minutes total, flipping carefully at 7 minutes and spritzing the second side with oil. The pancakes are done when both sides are deeply golden and the coating is crisp.
Serve immediately, topped with sour cream and extra scallions.