Preheat oven to 350 degrees.
Mix all brownie ingredients in a bowl and pour into a greased 8x8" pan.
Bake for 45 minutes, or until toothpick inserted comes out clean.
For muddy buddies, pour cereal into large bowl.
In 1-quart, microwave-safe bowl combine chocolate chips, peanut butter and margarine.
Microwave 1 to 1 1/2 minutes or until smooth, stirring after 1 minute.
Stir in vanilla.
Pour chocolate sauce slowly over cereal, stirring to coat evenly.
Pour cereal into large plastic bag. Add brownie mix (this would be from a second box of brownie mix) and secure; shake to coat well.
After the prepared brownies have cooled, cut into small bite sized squares and add to muddy buddies.
Spread on wax paper to cool.