Line a medium baking sheet with foil, parchment paper, or wax paper and set aside.
In a microwave safe bowl, heat the milk chocolate on high for 60 seconds. Stir, and then heat in 15 second intervals until just melted. Pour the melted chocolate onto the prepared baking sheet and use a spatual to spread over the entire area, into the corners, and getting it as even in thickness as you can.
Sprinkle the crushed pretzels over the entire area, as evenly as possible. Place in the refrigerator (or freezer if you're pressed for time) to firm up for about 10 minutes.
In a second bowl, repeat the melting process with the white chocolate. Pour over the hardened chocolate and pretzel layer, and spread to cover the entire area.
In rows or design pattern of your choice, place dots, at leasts an inch apart, in varying colors across the white chocolate surface. Use a toothpick and drag the tip through the colors, to create streaks or swirls - again, in the pattern of your choosing. I placed my dots in rows and dragged the toothpick through sideways, and then again top-to-bottom, to create a swirly look.
Now sprinkle the M&M's across the top, and then the sprinkles. refrigerate (or freeze) for 15 minutes to firm up and then you can break apart - using a knife or your hands! The pieces don't need to be uniform in size or shape, so have fun with it! These will keep for a couple of weeks in an airtight container, but it won't last that long!