Preheat oven to 375°F (190°C). Using a hand mixer on medium speed or a whisk, cream together butter and sugars until light and fluffy, then add the egg and vanilla. Mix until just combined.
In a large bowl, combine flour, coconut, oats, baking soda and salt. Add the flour mixture to the butter mixture, stirring with a wooden spoon until combined. Blend in pretzels, chocolate and cereal until just combined.
Drop about 30 spoonfuls of cookie dough, roughly 2 in. (5 cm) apart, onto parchment paper-lined baking sheets. Bake in centre of oven, 8 min. for chewy cookies, 10 min. for crisp ones. Cool on wire racks.