Yes! In a large microwave-safe large bowl, melt the butter and the marshmallows for about 2-3 minutes. The marshmallows will expand as they heat up. Once they have melted, remove the bowl from the microwave, and stir the butter into the marshmallows, making sure they are completely melted. Pour in the Fruity Pebbles, and quickly stir them in, until they are coated with the melted marshmallows.