Line a baking sheet with parchment paper and arrange Oreo cookies in a single layer.
Melt semi-sweet chocolate chips in 20-second microwave intervals, stirring until smooth.
Dip each Oreo into melted chocolate using a fork and tap to remove excess coating.
Place coated cookies onto the parchment-lined baking sheet.
Add sprinkles or toppings while the chocolate is still wet.
Melt white chocolate and drizzle over the cookies.
Let cookies sit at room temperature for 30 minutes or refrigerate for 10–15 minutes.