Line a large baking sheet with parchment paper and set it within reach of the stove.

In a very large bowl, combine the rice cereal squares, pretzel twists and oat cereal rings, tossing gently so nothing crushes.

Melt the white chocolate wafers in a microwave safe bowl in 30 second bursts, stirring between each, until smooth and pourable, about 2 minutes total.

Pour the melted white chocolate over the cereal mixture and fold gently with a spatula until every piece is lightly coated and no dry patches remain.

Scatter the candy coated chocolates over the top and fold once or twice more, just enough to distribute them without crushing the cereal.

Spread the mixture in a thin, even layer across the lined baking sheet, breaking up any large clumps with the spatula.

Scatter the sprinkles over the top while the coating is still wet, so they stick rather than roll off.

Let the mixture set at room temperature for 15 minutes, or until the white chocolate is firm and no longer glossy, then break into irregular clusters by hand.