Line a 9x9 pan with parchment paper and set aside. In a medium-sized pot, melt butter over medium heat.
Add your marshmallows and peanut butter to the pan and mix until completely melted. Remove from heat.
Fold cheerios into the marshmallow mixture. Once all of the ingredients are combined, pour into lined pan and pat down so that the surface is even. Allow to set for about an hour.
Once set, place the treats on a larger baking sheet (it'll be easier to work with) and cut into rectangles.
Melt chocolate chips and drizzle onto each Cheerio treat with a piping bag. Use the remainder of your chocolate to "glue on" your pretzel so that it sticks right on top of your Cheerio treat.
Allow the chocolate to set then serve and enjoy.