If you want to defrost frozen muffins, you have a few options depending on how much time you have: in the fridge overnight, unwrapped to avoid moisture buildup on the surface of the muffin tops; at room temperature, unwrapped to avoid moisture buildup on the surface of the muffin tops—this will take at least 30 minutes; in the microwave oven: place the unwrapped muffin on a napkin or a microwave-safe plate. Microwave on HIGH for about 30 seconds for each muffin. The time and results will vary according to the power of your microwave. I suggest microwaving in short increments to avoid drying out the muffins or burning them.