In a food processor or blender, combine watermelon, strawberries, honey, vanilla extract and mint leaves. Blend well.
(optional) You may strain the mixture in a strainer or cheese cloth if you’d prefer to get rid of any extra seeds.
Pour mixture in Popsicle molds about 3/4 of the way full and spoon Greek yogurt the rest of the way. Use a chopstick, knife, or anything you have on hand to create a sort of marbling effect with the Greek yogurt. Not necessary, but pretty!