In the bowl of a food processor fitted with the metal blade, puree bananas until smooth. Add yogurt, sugar, and lemon juice; pulse to combine. Remove 1/2 of the yogurt mixture; set aside.
Add blueberries to processor and pulse until just combined. Layer blueberry and reserved yogurt mixtures into 10 (1/3 cup) popsicle molds. Using a wooden skewer, swirl the 2 flavors together. Insert popsicle sticks. Freeze until frozen, about 8 hours.
Dip molds quickly in hot water to unmold.
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