Unwrap Rice Krispie Treats (or cut homemade into 3x2-inch rectangles).
Melt candy melts or bark coating in microwave as instructed (typically in 30 second batches, stirring throughout) and mix together with shortening.
Dip desired amount of each Rice Krispie Treats into candy coating. Let excess drip back into container to prevent waste. Sprinkle with Christmas sprinkles or M&Ms until desired amount is reached.
Place treats on wax paper and let sit until coating has begun to set.
Store in an airtight container (lasts for up to 2 weeks).