Slice watermelon into ¼ to ½ inch pieces. Using a star fruit cutter or cookie cutter, firmly press down, then press the shape out. Set aside cut-out watermelon stars.
Slice strawberries in half.
Assemble the kebabs by adding a watermelon star first, then a blueberry, mini marshmallow, blackberry, and strawberry half. Slightly angle the strawberry half so it fits nicely.