Add the Oreo cookies to a food processor and process until they become fine crumbs. Transfer the crumbs to a large mixing bowl and add the softened cream cheese and vanilla extract. Mix with a sturdy spatula or clean hands until a soft, uniform dough forms. Regular Oreos work best for this recipe, as Double Stuf cookies can make the mixture too soft.

Use a 1-tablespoon cookie scoop to portion the mixture, then roll each portion into a smooth ball. Arrange the truffles on a wax paper- or parchment-lined baking sheet.

Working with one candy color at a time, melt about 3 ounces (half of one color) of candy melts in a microwave-safe bowl at 50% power for 1 minute. Stir well, then continue heating in 20- to 30-second intervals, stirring after each, until completely smooth. If the candy melts begin to thicken while you're working, microwave for another 10 to 15 seconds and stir again.

Melt the white candy melts at 50% power for 30 seconds, stir well, then continue heating in 15-second intervals until smooth. Transfer the melted candy to a small zip-top bag or piping bag and snip a tiny corner.

Working with just a few truffles at a time, drizzle the white candy melts over the tops, then immediately add the rainbow nonpareil sprinkles before the drizzle hardens.

Allow the truffles to stand until the coating is completely set, or refrigerate for about 30 minutes to speed up the process.

Serve immediately, or store the truffles in an airtight container in the refrigerator for up to 1 week. To freeze, place the truffles in a single layer until frozen solid, then transfer them to a freezer-safe container or bag for up to 2 months. Thaw overnight in the refrigerator before serving to help prevent condensation from forming on the candy coating.